Refereed Publications
Year Author Word



2003

Aldrian, E. and R. D. Susanto, 2003: Identification of three dominant rainfall regions within Indonesia and their relationship to sea surface temperature. International Journal of Climatology, 23(12): 1435-1452. ABS
Armstrong, A. E., L. B. Tremblay and L. A. Mysak, 2003: A data-model intercomparison study of Arctic sea-ice variability. Climate Dynamics, 20(5): 465-476. PDF ABS
Basher, R. and M. A. Cane, 2003: Climate Variability, Climate Change and Malaria. In: E. Casman and H. Dowlatabadi (Editors), The contextual determinants of malaria. Resources for the Future, Washington D.C, pp. 189-215.
Biasutti, M., D. S. Battisti and E. S. Sarachik, 2003: The annual cycle over the tropical Atlantic, South America, and Africa. Journal of Climate, 16(15): 2491-2508. PDF ABS
Boelman, N. T., M. Stieglitz, H. M. Rueth, M. Sommerkorn, K. L. Griffin, G. R. Shaver and J. A. Gamon, 2003: Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra. Oecologia, 135(3): 414-421. ABS
Burnett, W. H., V. M. Kamenkovich, A. L. Gordon and G. L. Mellor, 2003: The Pacific/Indian Ocean pressure difference and its influence on the Indonesian Seas circulation: Part I - The study with specified total transports. Journal of Marine Research, 61(5): 577-611. ABS
Camargo, S. J., 2003: Western North Pacific typhoon season. State of the Climate in 2002, 84(6): S26-S28.
Chen, D., 2003: A comparison of wind products in the context of ENSO prediction. Geophysical Research Letters, 30(3): 1107-1110. ABS
Chen, D., H. W. Ou and C. M. Dong, 2003: A model study of internal tides in coastal frontal zone. Journal of Physical Oceanography, 33(1): 170-187. ABS
Chen, D., W. T. Liu, W. Q. Tang and Z. R. Wang, 2003: Air-sea interaction at an oceanic front: Implications for frontogenesis and primary production. Geophysical Research Letters, 30(14): 1745, doi:10.1029/2003GL017536. ABS
Chiang, J. C. H., M. Biasutti and D. S. Battisti, 2003: Sensitivity of the Atlantic ITCZ to Last Glacial Maximum boundary conditions. Paleoceanography, 18: 10.1029/2003PA000916 (11 Dec 2003). PDF
Cullather, R. I. and A. H. Lynch, 2003: The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North Pole. International Journal of Climatology, 23(10): 1161-1183. ABS
Egger, J. , K. P. Hoinka, K. Weickmann and H. P. Huang, 2003: Angular momentum budgets based on NCEP and ECMWF reanalysis data: an intercomparison. Monthly Weather Review, 131: 2577-2585.
Emile-Geay, J., M. A. Cane, N. H. Naik(Henderson), R. Seager, A. C. Clement and A. van Geen, 2003: Warren revisited: Atmospheric freshwater fluxes and "Why is no deep water formed in the North Pacific''. Journal of Geophysical Research-Oceans, 108(C6): 3178, doi: 10.1029/2001JC001058. PDF ABS
Feingold, G., W. L. Eberhard, D. E. Veron and M. Previdi, 2003: First measurements of the Twomey indirect effect using ground-based remote sensors. Geophysical Research Letters, 30(6): -. ABS
Gat, J. R., B. Klein, Y. Kushnir, W. Roether, H. Wernli, R. Yam and A. Shemesh, 2003: Isotope composition of air moisture over the Mediterranean Sea: an index of the air-sea interaction pattern. Tellus Series B-Chemical and Physical Meteorology, 55(5): 953-965. ABS
Gildor, H., A. H. Sobel, M. A. Cane and R. N. Sambrotto, 2003: A role for ocean biota in tropical intraseasonal atmospheric variability. Geophysical Research Letters, 30(9): 1624, doi:10.1029/2002GL016759. PDF ABS
Gildor, H., A. H. Sobel, M. A. Cane and R. N. Sambrotto, 2003: Correction to "A role for ocean biota in tropical intraseasonal atmospheric variability". Geophysical Research Letters, 30(12): 1624, doi:10.1029/2003GL017803. PDF ABS
Gordon, A. L., 2003: Oceanography - The brawniest retroflection. Nature, 421(6926): 904-905.
Gordon, A. L., C. F. Giulivi and A. G. Ilahude, 2003: Deep topographic barriers within the Indonesian seas. Deep-Sea Research Part II-Topical Studies in Oceanography, 50(12-13): 2205-2228. PDF ABS
Gordon, A. L., R. D. Susanto and K. Vranes, 2003: Cool Indonesian throughflow as a consequence of restricted surface layer flow. Nature, 425(6960): 824-828. PDF ABS
Harnik, N. and E. K. M. Chang, 2003: Storm track variations as seen in radiosonde observations and reanalysis data. Journal of Climate, 16(3): 480-495. PDF ABS
Hein, J. R., E. T. Baker, J. P. Cowen, C. R. German, E. Holzbecher, R. A. Koski, M. J. Mottl, N. V. Pimenov, S. D. Scott and A. M. Thurnherr, 2003: How important are the material and energy fluxes from hydrothermal circulation to the ocean? In: P.E.V.T.J.R.H. Halbach (Editor), Energy and Mass Transfer in Marine Hydrothermal Systems. Dahlem University Press, Berlin, pp. 337-355.
Hohmann, R., P. Schlosser and B. Huber, 2003: Helium 3 and dissolved oxygen balances in the upper waters of the Weddell Sea: Implications for oceanic heat fluxes. Journal of Geophysical Research, 108(C3): 3087. ABS
Huang, H. P., K. M. Weickmann and R. D. Rosen, 2003: Unusual behavior in atmospheric angular momentum during the 1965 and 1972 El Niños. Journal of Climate, 16(15): 2526-2539. ABS
Kamenkovich, V. M., W. H. Burnett, A. L. Gordon and G. L. Mellor, 2003: The Pacific/Indian Ocean pressure difference and its influence on the Indonesian Seas circulation: Part II - The study with specified sea-surface heights. Journal of Marine Research, 61(5): 613-634. ABS
Kaplan, A., M. A. Cane and Y. Kushnir, 2003: Reduced space approach to the optimal analysis interpolation of historical marine observations: Accomplishments, difficulties, and prospects, Advances in the Applications of Marine Climatology: The Dynamic Part of the WMO Guide to the Applications of Marine Climatology, WMO/TD-1081. World Meteorological Organization, Geneva, Switzerland, pp. 199-216. LINK PDF ABS
Khatiwala, S., 2003: Generation of internal tides in an ocean of finite depth: analytical and numerical calculations. Deep-Sea Research Part I-Oceanographic Research Papers, 50(1): 3-21. ABS
Khodri, M., G. Ramstein, D. Paillard, J. C. Duplessy, M. Kageyama and A. Ganopolski, 2003: Modelling the climate evolution from the last interglacial to the start of the last glaciation: The role of Arctic Ocean freshwater budget. Geophysical Research Letters, 30(12): doi:10.1029/2003GL017108. ABS
Khodri, M., G. Ramstein, N. deNoblet-Ducoudre and M. Kageyama, 2003: Sensitivity of the northern extratropics hydrological cycle to the changing insolation forcing at 126 and 115 ky BP. Climate Dynamics, 21(3-4): 273-287. ABS
Krahmann, G. , M. Visbeck, W. Smethie, Eric A. D'Asaro, Peter B. Rhines, R. Allyn Clarke, John Lazier, Russ E. Davis, Pearn P. Niiler, Peter S. Guest, Jens Meincke, G. W. Kent Moore, Robert S. Pickart, W. B. Owens, Mark D. Prater, Ian A. Renfrew and Friedrich A. Schott, 2003: The Labrador Sea Deep Convection Experiment data collection. Geochemistry Geophysics Geosystems, 4(10): 1091, doi:10.1029/2003GC000536. PDF ABS
Krahmann, G. and M. Visbeck, 2003: Arctic Ocean sea ice response to Northern Annular Mode-like wind forcing. Geophysical Research Letters, 30(15): 1793, doi:10.1029/2003GL017354. PDF ABS
Krahmann, G. and M. Visbeck, 2003: Variability of the Northern Annular Mode's signature in winter sea ice concentration. Polar Research, 22(1): 51-57. PDF ABS
Lin, X. H., J. E. Smerdon, A. W. England and H. N. Pollack, 2003: A model study of the effects of climatic precipitation changes on ground temperatures. Journal of Geophysical Research-Atmospheres, 108(D7): doi:10.1029/2002JD002878. PDF ABS
Liu, J. P., G. A. Schmidt, D. G. Martinson, D. Rind, G. Russell and X. J. Yuan, 2003: Sensitivity of sea ice to physical parameterizations in the GISS global climate model. Journal of Geophysical Research-Oceans, 108(C2): doi:10.1029/2001JC001167. PDF ABS
Martinson, D. G. and R. A. Iannuzzi, 2003: Spatial/temporal patterns in Weddell gyre characteristics and their relationship to global climate. Journal of Geophysical Research-Oceans, 108(C4): doi:10.1029/2000JC000538. PDF ABS
Ou, H. W., C. M. Dong and D. Chen, 2003: Tidal diffusivity: A mechanism for frontogenesis. Journal of Physical Oceanography, 33(4): 840-847. ABS
Perlwitz, J. and N. Harnik, 2003: Observational evidence of a stratospheric influence on the troposphere by planetary wave reflection. Journal of Climate, 16(18): 3011-3026. PDF ABS
Pollack, H. N., D. Y. Demezhko, A. D. Duchkov, I. V. Golovanova, S. P. Huang, V. A. Shchapov and J. E. Smerdon, 2003: Surface temperature trends in Russia over the past five centuries reconstructed from borehole temperatures. Journal of Geophysical Research-Solid Earth, 108(B4): doi:10.1029/2002JB002154. PDF ABS
Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. Journal of Geophysical Research-Atmospheres, 108(D14): doi:10.1029/2002JD002670. PDF ABS
Robertson, R., A. Beckmann and H. Hellmer, 2003: M-2 tidal dynamics in the Ross Sea. Antarctic Science, 15(1): 41-46. ABS
Rosenzweig, C., W. Baethgen, A. J. Busalacchi, M. A. Cane, D. Rind and C.J. Tucker, 2003: Using earth science tools to improve seasonal climate prediction for agriculture. Earth Observation Magazine, March/April: 32-35.
Seager, R. , R. Murtugudde, A. C. Clement and C. Herweijer, 2003: Why is there an evaporation minimum at the Equator? J. Climate, 16: 3792-3801. PDF
Seager, R., N. Harnik, Y. Kushnir, W. Robinson and J. Miller(Nakamura), 2003: Mechanisms of hemispherically symmetric climate variability. Journal of Climate, 16(18): 2960-2978. PDF ABS
Seager, R., R. Murtugudde, N. H. Naik(Henderson), A. Clement, N. Gordon and J. Miller(Nakamura), 2003: Air-sea interaction and the seasonal cycle of the subtropical anticyclones. Journal of Climate, 16(12): 1948-1966. PDF ABS
Shaman, J., J. F. Day and M. Stieglitz, 2003: St. Louis encephalitis virus in wild birds during the 1990 South Florida epidemic: The importance of drought, wetting conditions, and the emergence of Culex nigripalpus (Diptera : Culicidae) to arboviral amplification and transmission. Journal of Medical Entomology, 40(4): 547-554. ABS
Shaman, J., M. Stieglitz, S. Zebiak and M. A. Cane, 2003: A local forecast of land surface wetness conditions derived from seasonal climate predictions. Journal of Hydrometeorology, 4(3): 611-626. PDF ABS
Smerdon, J. E., H. N. Pollack, J. W. Enz and M. J. Lewis, 2003: Conduction-dominated heat transport of the annual temperature signal in soil. Journal of Geophysical Research-Solid Earth, 108(B9): doi:10.1029/2002JB002351. PDF ABS
Smith, R. C. , X. J. Yuan, J. Liu, D. G. Martinson and S. E. Stammerjohn, 2003: The Quasi-Quintennial Time Scale Climate Variability and Ecological Response. In: D. Greenland, D. Goodin and R.C. Smith (Editors), Climate Variability and Ecological Response. Oxford University Press, pp. 196-206.
Smith, R. C., W. R. Fraser and S. E. Stammerjohn, 2003: Climate variability and ecological response of the marine ecosystem in the western Antarctic Peninsula (WAP) region. In: D. Greenland, D.G. Goodin and R.C. Smith (Editors), Climate Variability and Ecosystem Response at Long-Term Ecological Research (LTER) Sites. Oxford University Press, New York, pp. 158-173.
Smith, R. C., W. R. Fraser, S. E. Stammerjohn and M. Vernet, 2003: Palmer Long-Term Ecological Research on the Antarctic marine ecosystem. In: E.W. Domack et al. (Editors), Antarctic Peninsula Climate Variability: Historical and Paleoenvironmental Perspectives. Antarctic Research Series. American Geophysical Union, Washington D.C., pp. 131-144.
Speer, K. G., M. E. Maltrud and A. M. Thurnherr, 2003: A Global View of Dispersion Above the Mid-Ocean Ridge. In: P.E. Halbach, V. Tunnicliffe and J.R. Hein (Editors), Energy and Mass Transfer in Marine Hydrothermal Systems. Dahlem University Press, Berlin, pp. 287-302. PDF
Stammerjohn, S. E., M. R. Drinkwater, R. C. Smith and X. Liu, 2003: Ice-atmosphere interactions during sea-ice advance and retreat in the western Antarctic Peninsula region. Journal of Geophysical Research, 108(C10): 10.1029/2002JC001543.
Stieglitz, M., S. J. Dery, V. E. Romanovsky and T. E. Osterkamp, 2003: The role of snow cover in the warming of arctic permafrost. Geophysical Research Letters, 30(13): doi:10.1029/2003GL017337,. ABS
Thurnherr, A. M. and K. G. Speer, 2003: Boundary mixing and topographic blocking on the Mid-Atlantic Ridge in the South Atlantic. Journal of Physical Oceanography, 33(4): 848-862. PDF ABS
Visbeck, M. , E. Chassignet, R. Curry, T. Delworth, B. Dickson and G. Krahmann, 2003: The Ocean's Response to North Atlantic Oscillation Variability. In: J. Hurrell, Y. Kushnir, G. Ottersen and M. Visbeck (Editors), The North Atlantic Oscillation. AGU monograph, Washington, pp. 113-146. PDF
Wajsowicz, R. C., A. L. Gordon, A. Ffield and R. D. Susanto, 2003: Estimating transport in Makassar Strait. Deep-Sea Research Part II-Topical Studies in Oceanography, 50(12-13): 2163-2181. ABS
Zappa, C. J., P. A. Raymond, E. A. Terray and W. R. McGillis, 2003: Variation in surface turbulence and the gas transfer velocity over a tidal cycle in a macro-tidal estuary. Estuaries, 26(6): 1401-1415. ABS



Abstracts

Aldrian, E. and R. D. Susanto, 2003: Identification of three dominant rainfall regions within Indonesia and their relationship to sea surface temperature. International Journal of Climatology, 23(12): 1435-1452.

The characteristics of climatic rainfall variability in Indonesia are investigated using a double correlation method. The results are compared with empirical orthogonal function (EOF) and rotated EOF methods. In addition, local and remote responses to sea-surface temperature (SST) are discussed. The results suggest three climatic regions in Indonesia with their distinct characteristics. Region A is located in southern Indonesia from south Sumatera to Timor island, southern Kalimantan, Sulawesi and part of Irian Jaya. Region B is located in northwest Indonesia from northern Sumatra to northwestern Kalimantan. Region C encompasses Maluku and northern Sulawesi. All three regions show both strong annual and. except Region A, semi-annual variability. Region C shows the strongest El Niño-southern oscillation (ENSO) influence, followed by Region A. In Region B, the ENSO-related signal is suppressed. Except for Region B, there are significant correlations between SST and the rainfall variabilities, indicating a strong possibility for seasonal climate predictions. March to May is the most difficult season to predict the rainfall variability. From June to November, there are significant responses of the rainfall pattern to ENSO in Regions A and C. A strong ENSO influence during this normally dry season (June to September) is hazardous in El Niño years, because the negative response means that higher SST in the NINO3 of the Pacific region will lower the rainfall amount over the Indonesian region. Analyses of Indonesian rainfall variability reveal some sensitivities to SST variabilities in adjacent parts of the Indian and Pacific Oceans. Copyright (C) 2003 Royal Meteorological Society.


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Armstrong, A. E., L. B. Tremblay and L. A. Mysak, 2003: A data-model intercomparison study of Arctic sea-ice variability. Climate Dynamics, 20(5): 465-476.

The dynamic-thermodynamic granular rheology sea-ice model of Tremblay and Mysak is validated against 40 years of observed sea-ice concentration (SIC) data. Subsequently, the mechanisms responsible, for producing SIC anomalies in the model are evaluated by studying the coupled variance (using the singular value decomposition method, SVD) between the simulated SIC anomalies and the ice speed and air temperature anomalies. To execute this validation, a 49-year (1949-97) simulation (including a 9-year spin-up period) of the Arctic and peripheral sea-ice cover using daily varying winds and monthly mean air temperatures is produced. In general, the simulated SIC variations for 1958-97 in the East Siberian, Chukchi and Beaufort seas are in agreement with observations, while larger discrepancies occur in the Laptev and Kara seas. Moreover, the sensitivity of the model to southerly wind anomalies in creating summer SIC anomalies compares well with the observed sensitivity; however, the model's sensitivity to summer air temperature anomalies is weaker than observed. The summer SIC anomalies over an entire sea are not influenced by variations in the level of river runoff. Results from the SVD analysis show that the main source of variability in the peripheral seas is associated with the variation in the strength of the Arctic High; in the East Siberian and Laptev seas, the strengthening and weakening of the Transpolar Drift Stream also play an important role. Over the entire Arctic domain, surface air temperature anomalies are negatively correlated with sea-ice anomalies. Finally, the observed downward trend in total sea-ice cover in the last two decades as well as record minima in the East Siberian Sea are well reproduced in the simulation.


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Biasutti, M., D. S. Battisti and E. S. Sarachik, 2003: The annual cycle over the tropical Atlantic, South America, and Africa. Journal of Climate, 16(15): 2491-2508.

The annual cycle over land can be thought of as being forced locally by the direct action of the sun and remotely by circulations forced by regions of persistent precipitation organized primarily by SST and, secondarily, by land. This study separates these two sources of annual variability in order to indicate where and when the remote effects are important.

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Boelman, N. T., M. Stieglitz, H. M. Rueth, M. Sommerkorn, K. L. Griffin, G. R. Shaver and J. A. Gamon, 2003: Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra. Oecologia, 135(3): 414-421.

This study explores the relationship between the normalized difference vegetation index (NDVI), aboveground plant biomass, and ecosystem C fluxes including gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem production. We measured NDVI across long-term experimental treatments in wet sedge tundra at the Toolik Lake LTER site, in northern Alaska. Over 13 years, N and P were applied in factorial experiments (N, P and N + P), air temperature was increased using greenhouses with and without N + P fertilizer, and light intensity (photosynthetically active photon flux density) was reduced by 50% using shade cloth. Within each treatment plot, NDVI, aboveground biomass and whole-system CO,! flux measurements were made at the same sampling points during the peak-growing season of 2001. We, found that across all treatments, NDVI is correlated with aboveground biomass (r(2)=0.84), GEP (r(2)=0.75) and ER (r(2)=0.71), providing a basis for linking remotely sensed NDVI to aboveground biomass and ecosystem carbon flux.


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Burnett, W. H., V. M. Kamenkovich, A. L. Gordon and G. L. Mellor, 2003: The Pacific/Indian Ocean pressure difference and its influence on the Indonesian Seas circulation: Part I - The study with specified total transports. Journal of Marine Research, 61(5): 577-611.

The main objective of this paper is to investigate the overall balance of momentum and energy within the Indonesian Seas to better understand the factors that control the total transport of the Indonesian Throughflow. Two models are used in the investigation: a "first-step" heuristic channel model and a more sophisticated "second-step," barotropic numerical model that incorporates high-resolution coastline and bottom topography. The experiments show that the barotropic model develops typical horizontal circulation patterns for the region. An analysis of the overall momentum and energy balances suggests that the total transport of the Indonesian Throughflow does not depend exclusively on the inter-ocean pressure difference but on other factors, including local winds, bottom form stresses, and the resultant of pressure forces acting on the internal sides.


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Chen, D., 2003: A comparison of wind products in the context of ENSO prediction. Geophysical Research Letters, 30(3): 1107-1110.

Four different wind products are evaluated in terms of their application to ENSO prediction. These wind products have been used to initialize an intermediate ocean-atmosphere coupled model for monthly retrospective forecasts from 1980 to 2002. The wind product that includes satellite scatterometer data has the highest scores, with the NCEP reanalysis and the new FSU objective analysis closely behind. The latter is a major improvement over the old FSU subjective analysis which has some serious problems in recent years. It seems that the wind products from remote sensing, in-situ observation and model reanalysis are all useful for ENSO prediction. At present, an ensemble of forecasts initialized with various wind data sets is probably our best bet.


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Chen, D., H. W. Ou and C. M. Dong, 2003: A model study of internal tides in coastal frontal zone. Journal of Physical Oceanography, 33(1): 170-187.

Internal tides near a midlatitude shelf-slope front are studied using an idealized numerical model, with emphasis on their structure, energetics, and mixing effects. It is found that the properties of internal tides are highly dependent on frontal configuration and tidal frequency. At a winter front, energetic internal tides are generated and arrested in the frontal zone; the cross-shelf flow tends to be surface (bottom) intensified by a large internal circulation cell at the diurnal (semidiurnal) frequency. At a summer front, the diurnal internal tide is still trapped, but a semidiurnal internal tide propagates out of the frontal zone in the offshore direction while arrested at the inshore boundary. The presence of the shelf-slope front enhances the generation of internal tides, and it also causes an amplification of the semidiurnal internal tide by trapping its energy in the frontal zone. This amplification is most prominent at the offshore boundary of the winter front and the inshore boundary of the summer front, where strong tidal refraction takes place. Internal tides can cause significant mixing and dispersion in the frontal zone, with the semidiurnal internal tide being most effective toward the frontal boundaries, and the diurnal internal tide more effective near the site of generation.


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Chen, D., W. T. Liu, W. Q. Tang and Z. R. Wang, 2003: Air-sea interaction at an oceanic front: Implications for frontogenesis and primary production. Geophysical Research Letters, 30(14): 1745, doi:10.1029/2003GL017536.

Based on recent satellite observations, we hypothesize that there exists a significant air-sea interaction at the shelf-break front in the East China Sea. An idealized ocean-atmosphere coupled model was designed to test this hypothesis and to study the physical processes involved in such an interaction, with emphasis on the oceanic part. A positive feedback between ocean and atmosphere was identified in the model and its consequences were evaluated. We found that air-sea interaction, when combined with sloping topography, could provide a mechanism for the genesis of the shelf-break front. The resulting frontal circulation and vertical mixing could bring nutrient-rich subsurface water into the surface euphotic zone, thus making the frontal region a conspicuous place for primary production.


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Cullather, R. I. and A. H. Lynch, 2003: The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North Pole. International Journal of Climatology, 23(10): 1161-1183.

A comparison of National Centers for Environmental Prediction - National Center for Atmospheric Research reanalysis six-hourly sea-level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950-91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin-Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence p of the semiannual variation over time is highly variable.

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Emile-Geay, J., M. A. Cane, N. H. Naik(Henderson), R. Seager, A. C. Clement and A. van Geen, 2003: Warren revisited: Atmospheric freshwater fluxes and "Why is no deep water formed in the North Pacific''. Journal of Geophysical Research-Oceans, 108(C6): 3178, doi: 10.1029/2001JC001058.

Warren's [1983] "Why is no deep water formed in the North Pacific'' is revisited. His box model of the northern North Pacific is used with updated estimates of oceanic volume transports and boundary freshwater fluxes derived from the most recent data sets, using diverse methods. Estimates of the reliability of the result and its sensitivity to error in the data are given, which show that the uncertainty is dominated by the large observational error in the freshwater fluxes, especially the precipitation rate. Consistent with Warren's conclusions, it is found that the subpolar Atlantic-Pacific salinity contrast is primarily explained by the small circulation exchange between the subpolar and subtropical gyres, and by the local excess of precipitation over evaporation in the northern North Pacific. However, unlike Warren, we attribute the latter excess to atmospheric water vapor transports, in particular the northern moisture flux associated with the Asian Monsoon. Thus the absence of such a large transport over the subpolar North Atlantic may partly explain why it is so salty, and why deep water can form there and not in the North Pacific.


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Feingold, G., W. L. Eberhard, D. E. Veron and M. Previdi, 2003: First measurements of the Twomey indirect effect using ground-based remote sensors. Geophysical Research Letters, 30(6): -.

[1] We demonstrate first measurements of the aerosol indirect effect using ground-based remote sensors at a continental US site. The response of nonprecipitating, ice-free clouds to changes in aerosol loading is quantified in terms of a relative change in cloud-drop effective radius for a relative change in aerosol extinction under conditions of equivalent cloud liquid water path. This is done in a single column of air at a temporal resolution of 20 s (spatial resolution of similar to100 m). Cloud-drop effective radius is derived from a cloud radar and microwave radiometer. Aerosol extinction is measured below cloud base by a Raman lidar. Results suggest that aerosols associated with maritime or northerly air trajectories tend to have a stronger effect on clouds than aerosols associated with northwesterly trajectories that also have local influence. There is good correlation (0.67) between the cloud response and a measure of cloud turbulence.


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Gat, J. R., B. Klein, Y. Kushnir, W. Roether, H. Wernli, R. Yam and A. Shemesh, 2003: Isotope composition of air moisture over the Mediterranean Sea: an index of the air-sea interaction pattern. Tellus Series B-Chemical and Physical Meteorology, 55(5): 953-965.

The isotope composition of atmospheric moisture over the Mediterranean Sea, collected during the cruise of the research vessel meteor in January 1995. confirmed that the intensive air-sea interaction near the coast under conditions of a large humidity deficit labels the resultant atmospheric waters with a large deuterium-excess parameter. The present data set shows this effect to result both when cold air from the European continent moves over the sea as well as when warm and dry air from North Africa is involved. The situation in the eastern and western Mediterranean differ in the vertical structure of the isotope composition further away from the coast. as expressed by the gradients of the d(excess) values with altitude over the sea surface. i.e. increasing with attitude in the eastern Mediterranean, whereas the opposite effect is noted in the western section and near the coast. A comparison of the isotopic composition of the samples with the expected buildup of moisture over the sea. based on the Craig-Gordon model. suggests that up to one half of the added moisture may have resulted at times from the evaporation of sea-spray droplets, without any significant isotope fractionation, in addition to the vapour-mediated transport from the sea Surface. which favors the lighter isotopic species.


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Gildor, H., A. H. Sobel, M. A. Cane and R. N. Sambrotto, 2003: A role for ocean biota in tropical intraseasonal atmospheric variability. Geophysical Research Letters, 30(9): 1624, doi:10.1029/2002GL016759.

We propose that temporal variations within the marine plankton system can induce intraseasonal variations in sea surface temperature (SST) through the effect on solar penetration due to chlorophyll and other optically active organic components. Sensitivity studies with a simple model suggest that these small oscillations in SST may stimulate radiative-convective oscillations in the atmosphere which amplify them and thus induce or modulate significant variability in the coupled system. Long term bio-optical measurements in the Western Pacific, where satellite time series are degraded by clouds, would provide a test of our theory and would improve our understanding of the heat balance in this climatically important region.


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Gildor, H., A. H. Sobel, M. A. Cane and R. N. Sambrotto, 2003: Correction to "A role for ocean biota in tropical intraseasonal atmospheric variability". Geophysical Research Letters, 30(12): 1624, doi:10.1029/2003GL017803.

We propose that temporal variations within the marine plankton system can induce intraseasonal variations in sea surface temperature (SST) through the effect on solar penetration due to chlorophyll and other optically active organic components. Sensitivity studies with a simple model suggest that these small oscillations in SST may stimulate radiative-convective oscillations in the atmosphere which amplify them and thus induce or modulate significant variability in the coupled system. Long term bio-optical measurements in the Western Pacific, where satellite time series are degraded by clouds, would provide a test of our theory and would improve our understanding of the heat balance in this climatically important region.


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Gordon, A. L., C. F. Giulivi and A. G. Ilahude, 2003: Deep topographic barriers within the Indonesian seas. Deep-Sea Research Part II-Topical Studies in Oceanography, 50(12-13): 2205-2228.

Whereas at the surface and at thermocline depth the Indonesian throughflow can weave its way between basins towards the Indian Ocean on a quasi-horizontal plane, at greater depth numerous sills are encountered, resulting in circulation patterns governed by density-driven overflow processes. Pacific water spills over deep topographic barriers into the Sulawesi Sea and into the Seram and Banda seas. The western-most throughflow path flowing through Makassar Strait encounters shallower barriers than does the eastern path. The first barrier encountered by Pacific water directed towards Makassar Strait is the 1350-m deep Sangihe Ridge, providing access to the Sulawesi Sea. The 680-m deep Dewakang Sill separating the southern Makassar Strait from the Flores Sea is a more formidable barrier. Along the eastern path, Pacific water must flow over the 1940 m barrier of the Lifamatola Passage before passing into the deep levels of the Seram and Banda Seas. The deepest barrier encountered by both the western and eastern paths to the Indian Ocean is the 1300-1450 m (perhaps as deep as 1500 m) sill of the Sunda Arc near Timor. The Savu Sea while connected to the Banda Sea down to 2000 m depth, is closed to the Indian Ocean at a depth shallower than the Timor Sill. The density-driven overflows force upwelling of resident waters within the confines of the basins, which is balanced by diapycnal mixing, resulting in an exponential deep-water temperature profile. A scale depth (Z* = K-z/w) of 420-530 m is characteristic of the 300-1500 m depth range, with values closer to 600 m for the deeper water column. The upwelled water within the confines of the Banda Sea, once over the confining sill of the Sunda Arc, may contribute 1.8-2.3 Sv the interocean throughflow. (C) 2003 Elsevier Science Ltd. All rights reserved.


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Gordon, A. L., R. D. Susanto and K. Vranes, 2003: Cool Indonesian throughflow as a consequence of restricted surface layer flow. Nature, 425(6960): 824-828.

Approximately 10 million m(3) s(-1) of water flow from the Pacific Ocean into the Indian Ocean through the Indonesian seas(1). Within the Makassar Strait, the primary pathway of the flow(2), the Indonesian throughflow is far cooler than estimated earlier, as pointed out recently on the basis of ocean current and temperature measurements(3,4). Here we analyse ocean current and stratification data along with satellite-derived wind measurements, and find that during the boreal winter monsoon, the wind drives buoyant, low-salinity Java Sea surface water into the southern Makassar Strait, creating a northward pressure gradient in the surface layer of the strait. This surface layer 'freshwater plug' inhibits the warm surface water from the Pacific Ocean from flowing southward into the Indian Ocean, leading to a cooler Indian Ocean sea surface(5-7), which in turnmay weaken the Asian monsoon(8). The summer wind reversal eliminates the obstructing pressure gradient, by transferring more- saline Banda Sea surface water into the southern Makassar Strait. The coupling of the southeast Asian freshwater budget to the Pacific and Indian Ocean surface temperatures by the proposed mechanism may represent an important negative feedback within the climate system.


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Harnik, N. and E. K. M. Chang, 2003: Storm track variations as seen in radiosonde observations and reanalysis data. Journal of Climate, 16(3): 480-495.

The interannual variations in the Northern Hemisphere storm tracks during 1949-99 based on unassimilated radiosonde data are examined and compared to similarly derived quantities using the NCEP-NCAR reanalysis at sonde times and locations. This is done with the motivation of determining the extent to which the storm track variations in reanalysis data are real. Emphasis is placed on assessing previous findings, based on NCEP-NCAR reanalysis data, that both storm tracks intensified from the 1960s to the 1990s with much of the intensification occurring during the early 1970s, and that the Atlantic and Pacific storm tracks are significantly correlated.


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Hohmann, R., P. Schlosser and B. Huber, 2003: Helium 3 and dissolved oxygen balances in the upper waters of the Weddell Sea: Implications for oceanic heat fluxes. Journal of Geophysical Research, 108(C3): 3087.

We present helium 3 (He-3) and dissolved oxygen (DO) distributions in the upper waters of the central Weddell Sea obtained from samples collected during the Winter Weddell Sea Project (WWSP, July to September 1986), and the Antarctic Zone Flux Experiment (ANZFLUX, July to August 1994). The data are discussed in terms of apparent entrainment rates of Weddell Deep Water (WDW) into the Winter Mixed Layer (WML) and the associated apparent heat flux. The fraction of WDW in the WML derived from the He-3 excess (Deltadelta(3) He) and DO deficit in the mixed layer increases with latitude and reaches 10-20% at 68degreesS. The corresponding apparent heat flux during the winter entrainment period is 14 +/- 4 W m(-2), and the apparent annual heat flux is 6 +/- 4 W m(-2). Significantly larger heat fluxes ( winter ocean heat flux of 25 W m(-2); average annual heat flux of 15 W m(-2)) are observed near Maud Rise and in the region southwest of the rise in features that are associated with a Taylor column that apparently forms over the seamount. The entrainment rates and heat fluxes obtained from a one-dimensional numerical model exceed those calculated from the WDW fraction in the WML by about a factor of two, mainly because of the effect of gas exchange through leads on the mass balance of 3 He and DO in the WML. The best agreement between model calculations performed for 62.5degreesS, 65degreesS, and 67.5degreesS and observations is achieved for entrainment rates of 25-35 m yr(-1), 30-40 m yr(-1), and 35-45 m yr(-1), respectively. Daily entrainment rates are practically identical (0.28-0.39 m d(-1)) for the three latitudes. Corresponding simulated heat fluxes for the winter entrainment period and the annual average are 36-50 W m(-2) and 10-17 W m(-2), respectively. Extrapolation of the annual average heat flux to the seasonally ice-covered Weddell Sea yields a value of 0.04-0.07 PW.


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Huang, H. P., K. M. Weickmann and R. D. Rosen, 2003: Unusual behavior in atmospheric angular momentum during the 1965 and 1972 El Niños. Journal of Climate, 16(15): 2526-2539.

The global atmospheric angular momentum (AAM) is known to increase with tropical eastern Pacific sea surface temperature (SST) anomalies during El Nino events. Using a reanalysis dataset, the ratio of the monthly AAM anomaly to El Nino SST anomaly ( based on the Nino-3.4 index) is found to be approximately 1 angular momentum unit (=10(25) kg m(2) s(-1)) per degree Celsius for most post-1975 El Ninos. This ratio is much smaller, however, during the 1965/66 and 1972/73 El Ninos, raising the possibilities that either the early reanalysis data are in error due to sparse observations, or the atmospheric response to the two early El Ninos was unusual. The possibility of a severe data problem in the reanalysis is ruled out by cross-validating the AAM time series with independent measurements of length of day. The latitudinal structures of the zonal wind anomalies in 1965/66 and 1972/73 are examined for both the reanalysis and a set of general circulation model (GCM) simulations. Multiple GCM runs with specified SST produce a more positive ensemble-mean AAM anomaly in 1965 than its counterpart in the reanalysis. The GCM-simulated ensemble-mean zonal wind anomaly resembles the canonical El Nino response with accelerations of subtropical zonal jets in both hemispheres, a pattern that is almost absent in the reanalysis. On the other hand, a large spread exists among the individual ensemble members in the 1965/ 66 GCM simulations. Although the majority of the individual ensemble members shows the canonical El Nino response, two outliers ( out of 12 runs) exhibit very small zonal wind responses in the Northern Hemisphere similar to the reanalysis. Thus, the observed AAM anomaly during 1965/ 66 is interpreted as an outlier with atmospheric noise being strong enough to overwhelm the canonical El Nino response. The low AAM in the 1972/73 event is related in the reanalysis to a significantly negative zonal wind response on the equator. This signal is robustly reproduced, although with a slightly smaller amplitude, in the ensemble mean and all individual ensemble members in the GCM simulations. The small ensemble standard deviation and large ensemble-mean response on the equator indicate that the negative response is due to the lower-boundary forcing related to the SST anomaly. The fact that the AAM anomaly in 1972/73 is not well correlated with the Nino-3.4 index, then, indicates that SST anomalies outside the conventional El Nino region may be responsible for the low AAM. The uncharacteristically low values of global AAM in 1965/ 66 and 1972/73 contribute to a low mean for the decade before 1975, which, combined with high AAM in the post-1980 era, produces a significant upward trend in AAM in the second half of the twentieth century. If the weak AAM anomalies during the two pre-1975 El Ninos are due to random noise or incidental non-El Nino influences, taking them at face value would result in an overestimate of about 15% - 20% in the multidecadal trend of AAM due to boundary forcing alone. Notably, a multidecadal trend in AAM is also simulated in the ensemble mean of the multiple GCM runs, but its magnitude is smaller than the observed counterpart and more consistent with the multidecadal trend of the Nino-3.4 index. The implications of these findings for climate change detection are discussed.


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Kamenkovich, V. M., W. H. Burnett, A. L. Gordon and G. L. Mellor, 2003: The Pacific/Indian Ocean pressure difference and its influence on the Indonesian Seas circulation: Part II - The study with specified sea-surface heights. Journal of Marine Research, 61(5): 613-634.

In Part II we construct new numerical solutions to further analyze our results in Part I (Burnett et al., 2003), that indicate the lack of a unique relationship between the Pacific/Indian Ocean pressure difference and the total transport of the Indonesian Throughflow (ITF). These new solutions involve perturbations of the sea level relative to the original solutions. We present detailed analyses of the overall momentum and energy balances for these new solutions to stay consistent with the procedures developed in Part I. The results validate our conclusions regarding the lack of a unique relationship between the pressure head and the value of the total transport of the ITF. However, based on results from all the experiments, we have found that the seasonal variations of the total transport of the ITF are in phase with the pressure-head variations. Thus the hypothesis by Wyrtki (1987) that the pressure head, measured by the sea-surface-height difference between Davao (Philippines) and Darwin (Australia), is well correlated with the total transport is qualitatively supported.


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Kaplan, A., M. A. Cane and Y. Kushnir, 2003: Reduced space approach to the optimal analysis interpolation of historical marine observations: Accomplishments, difficulties, and prospects, Advances in the Applications of Marine Climatology: The Dynamic Part of the WMO Guide to the Applications of Marine Climatology, WMO/TD-1081. World Meteorological Organization, Geneva, Switzerland, pp. 199-216.

Observed historical climate fields are characterized by comparatively precise data and good coverage in the last few decades, and poor observational coverage prior. The technique of the reduced space optimal analysis of such fields (i.e. estimating them in projections onto a low-dimensional space spanned by the leading patterns of the signal variability) is presented in the context of more traditional approaches to data analysis. Advantages of the method are illustrated on examples of reconstructions of near-global monthly fields of sea surface temperature and sea level pressure from 1850s to present along with verified error bars. The limitations of the technique concerning quality and robustness of estimating a priori parameters, representation of long-term and small-scale types of variability, assumption of stationarity of means and covariances, and incompleteness of coverage are discussed, and possible ways to overcome these problems are suggested.


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Khatiwala, S., 2003: Generation of internal tides in an ocean of finite depth: analytical and numerical calculations. Deep-Sea Research Part I-Oceanographic Research Papers, 50(1): 3-21.

Mixing in the abyssal ocean is known to play an important role in controlling the large-scale ocean circulation. In the search for sources of mechanical energy for mixing, internal tides generated by the interaction of the barotropic tide with bottom topography (mode conversion) have been implicated. However, estimates of the rate at which barotropic tidal energy is converted into the internal wave field are quite uncertain. Here, I present analytical and numerical calculations of internal tide generation in a fluid layer of finite depth to better understand the energetics of the wave generation process. Previous theoretical models of wave generation have assumed an upper radiation boundary condition (BC) appropriate for an ocean of infinite depth. But recent observations of internal tides at significant distances from their generation region indicate that this BC is not always valid, and that reflection from the upper surface is important. I show that the presence of an upper free-surface reduces the rate at which energy is fed into the internal wave field (the power) and thus the energy available for mixing. This reduction increases with the horizontal extent of the topography (relative to the wavelength of a mode-1 internal wave). Fully nonhydrostatic, nonlinear numerical calculations are used to both test the theory and to explore more realistic parameters for which linear theories are formally invalid. As bottom topography becomes steeper, linear theory underestimates mode conversion by an increasing amount, although even at critical slope the difference is quite small (O(20%)). An important finding of this study is that for certain topographic shapes the power input into the wave field can saturate as the topography becomes supercritical. A comparison of model results with a recent finite amplitude theory suggests that even though finite depth effects may be negligible in the linear regime, they may become important when the topography is of finite amplitude. The results of process studies such as this should lead to improved estimates of mode conversion in the ocean. (C) 2003 Elsevier Science Ltd. All rights reserved.


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Khodri, M., G. Ramstein, D. Paillard, J. C. Duplessy, M. Kageyama and A. Ganopolski, 2003: Modelling the climate evolution from the last interglacial to the start of the last glaciation: The role of Arctic Ocean freshwater budget. Geophysical Research Letters, 30(12): doi:10.1029/2003GL017108.

The Earth's climate has alternated between glacial and interglacial stages, but we still do not understand how the changes in insolation have been amplified by the climate system to lead to such a large climatic response. Here we use a climate model of intermediate complexity to show that the orbitally induced shift from an interglacial to a preglacial climate is highly sensitive to the high northern latitudes moisture budget. Using the insolation forcing alone, the model produces a first order response of sea surface temperatures and thermohaline circulation evolution which agrees with the available geological data. Under the same gradual insolation evolution, adding a small freshwater input into the Arctic Ocean induces a rapid climate switch from an interglacial to a pre-glacial mode. These results suggest a simple connection between orbital forcing and the thermohaline circulation through a freshwater threshold within the ocean-atmosphere-sea-ice system.


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Khodri, M., G. Ramstein, N. deNoblet-Ducoudre and M. Kageyama, 2003: Sensitivity of the northern extratropics hydrological cycle to the changing insolation forcing at 126 and 115 ky BP. Climate Dynamics, 21(3-4): 273-287.

The orbital configuration at the end of the last interglacial, 115,000 years BP (115 ky BP), was such that the Northern Hemisphere seasonal contrast was decreased when compared to the last interglacial maximum, 126 ky BP. Climatic reconstructions argue for increased latitudinal surface temperature and salinity gradients in the North Atlantic at 115 ky BP compared to 126 ky BP. According to proxy measurements the high-latitude ocean freshening may be explained by enhanced northward atmospheric moisture advection which would have then led to decreased deep convection activity in the northern seas. To evaluate such re-adjustments of the atmospheric circulation to the insolation forcing changes, we have explored the changes in atmospheric energy balance and transport with two AGCM experiments, one for each climate. We show that the northward increase in static heat transport at 115 ky BP to 126 ky BP constitutes a first order response to the changing insolation. It tends to equalise the heat balance of the atmosphere. Despite sea surface temperatures fixed (SSTs) to present-day this feature is strongly amplified by the air-sea heat flux exchanges. By comparing with OAGCM experiments for the same periods, we find that the simulated surface ocean heat flux responses to insolation forcing are similar whether the ocean is allowed to vary or not. The latent heat transport does not undergo the same changes as the dry static one. On an annual basis, it decreases over the high northern latitudes. This is the result of summer modification of moisture sources and transient activity. The latter appears to affect latent heat transport much more than the dry static one. The winter response, however, differs from the summer response which dominates the annual mean. There is an enhanced northward atmospheric moisture advection during winter at 115 ky BP, which is responsible for the freshening of high-latitude ocean during this season. This result seems to confirm the hypothesis inferred from marine data.


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Krahmann, G. , M. Visbeck, W. Smethie, Eric A. D'Asaro, Peter B. Rhines, R. Allyn Clarke, John Lazier, Russ E. Davis, Pearn P. Niiler, Peter S. Guest, Jens Meincke, G. W. Kent Moore, Robert S. Pickart, W. B. Owens, Mark D. Prater, Ian A. Renfrew and Friedrich A. Schott, 2003: The Labrador Sea Deep Convection Experiment data collection. Geochemistry Geophysics Geosystems, 4(10): 1091, doi:10.1029/2003GC000536.

Between 1996 and 1998, a concerted effort was made to study the deep open ocean convection in the Labrador Sea. Both in situ observations and numerical models were employed with close collaboration between the researchers in the fields of physical oceanography, boundary layer meteorology, and climate. A multitude of different methods were used to observe the state of ocean and atmosphere and determine the exchange between them over the experiment's period. The Labrador Sea Deep Convection Experiment data collection aims to assemble the observational data sets in order to facilitate the exchange and collaboration between the various projects and new projects for an overall synthesis. A common file format and a browsable inventory have been used so as to simplify the access to the data.


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Krahmann, G. and M. Visbeck, 2003: Arctic Ocean sea ice response to Northern Annular Mode-like wind forcing. Geophysical Research Letters, 30(15): 1793, doi:10.1029/2003GL017354.

The response of the Arctic Ocean sea ice system to Northern Annular Mode-like wind forcing has been investigated using an ocean/sea ice general circulation model coupled to an atmospheric boundary layer model. A series of idealized experiments was performed to investigate the Arctic Ocean's response to idealized winter wind anomalies on interannual to multi-decadal time scales. The sea ice response of the model consists of a rapid change of ice movements leading to widespread variation in sea ice thickness and concentration. In most areas the response is largely independent of the forcing frequency with only a slight increase towards longer periods. Only the Greenland Sea exhibited a change in sign of sea ice concentration anomalies at about 20 years period which appears to be caused by slow adjustment of the oceanic circulation.


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Krahmann, G. and M. Visbeck, 2003: Variability of the Northern Annular Mode's signature in winter sea ice concentration. Polar Research, 22(1): 51-57.

Historical winter sea ice concentration data are used to examine the relation between the Northern Annular Mode (NAM) and the sea ice concentration in the Nordic seas over the past 50 years. The well known basic response pattern of a seesaw between the Labrador Sea and the Greenland, Iceland and Barents seas is being reproduced. However, the response is not robust in the Greenland and Iceland seas. There the observed variability has a more complex relationship with surface temperatures and winds. We divide the sea ice response into three spectral bands: high (P < 5 year), band (5 < P < 15 year), and low pass (P > 15 year) filtered NAM indices. This division is motivated by the expected slow response of the ocean circulation which might play a significant role in the Greenland and Iceland seas. The response to the NAM is also examined separately for the periods before and after 1976 to identify variations due to the relocation of the northern centre of the North Atlantic Oscillation.


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Lin, X. H., J. E. Smerdon, A. W. England and H. N. Pollack, 2003: A model study of the effects of climatic precipitation changes on ground temperatures. Journal of Geophysical Research-Atmospheres, 108(D7): doi:10.1029/2002JD002878.

[1] Temperature changes at the Earth surface propagate into the subsurface and leave a thermal signature in the underlying soil and rock. Inversions of subsurface temperature measurements yield reconstructions of ground surface temperature (GST) histories that provide estimates of climatic changes. A question remaining in the interpretation of reconstructed GST histories is the extent to which GST changes reflect changes principally in surface air temperature (SAT), or whether other factors may be significant. Here we use a Land Surface Processes (LSP) model to examine the influence of precipitation changes on GST and subsurface temperature and moisture fields on annual to decadal timescales. We model soil and vegetation conditions representative of a prairie region in the southern Great Plains of North America and force the model with meteorological data synthesized from a typical year in the region. Model responses are observed after changes in the amount of daily precipitation, the intensity and frequency of daily precipitation, and the diurnal and seasonal timing of precipitation. We show that: (1) increasing daily precipitation cools mean annual GST, (2) increasing the intensity and reducing the frequency of daily precipitation, while holding the annual amount of precipitation constant, cools mean annual GST, and (3) shifting maximum precipitation to occur in the warmest months cools mean annual GST. We compare modeled results to observed precipitation changes during the 20th century and conclude that the observed precipitation changes would cause only small changes to GST within the modeled region, on the order of 0.1 K or less.


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Liu, J. P., G. A. Schmidt, D. G. Martinson, D. Rind, G. Russell and X. J. Yuan, 2003: Sensitivity of sea ice to physical parameterizations in the GISS global climate model. Journal of Geophysical Research-Oceans, 108(C2): doi:10.1029/2001JC001167.

The GISS coupled model is used to investigate the sensitivity of sea ice to each of the following parameterizations: (1) two sea ice dynamics (CF: cavitating fluid; VP: viscous-plastic), (2) the specification of oceanic isopycnal mixing coefficients in the Gent and McWillams isopyncal mixing (GM), and (3) the wajsowicz viscosity diffusion (WV). The large-scale sea ice properties are highly sensitive to sea ice dynamics. With the inclusion of resistance to shear stress, VP captures the major observed sea ice drift features and improves the simulations of sea ice concentrations, thickness, and export through Fram Strait relative to CF. GM significantly improves the simulation of vertical temperature distributions in the Southern Ocean, although it leads to a dramatic reduction of Antarctic sea ice cover. The reduced oceanic isopycnal mixing coefficients lead to Arctic sea ice that tends to be less and thinner in almost the entire Arctic except in the North Pacific and Labrador Sea, while Antarctic sea ice that extends more equatorward throughout the circumpolar regions. The responses of sea ice to WV show an enlargement and thickening of sea ice in the Arctic, within the ice packs around the Antarctic and a reduction and thinning of sea ice in the northernWeddell and Ross Seas. On the basis of these experiments, two composite experiments with the best parameterizations are investigated. The atmospheric responses associated with sea ice changes are discussed. While improvements are seen, there are still many unrealistic aspects that will require further improvements to sea ice and ocean components.


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Martinson, D. G. and R. A. Iannuzzi, 2003: Spatial/temporal patterns in Weddell gyre characteristics and their relationship to global climate. Journal of Geophysical Research-Oceans, 108(C4): doi:10.1029/2000JC000538.

We examine the spatiotemporal variability of the upper ocean sea ice system of the Atlantic sector of the Southern Ocean subpolar seas (Weddell gyre) and the nature of its covariability with extrapolar climate. To systematically evaluate the sporadic and sparse distribution of subpolar data, we employed an optimal analysis involving empirical orthogonal functions (EOFs). The EOFs reveal that the pattern of spatial covariability of Weddell gyre characteristics is dominated by high interannual variability near the northern (circumpolar) rim of the gyre and lesser variability (10-20% of the variance) in the gyre's central core region.


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Ou, H. W., C. M. Dong and D. Chen, 2003: Tidal diffusivity: A mechanism for frontogenesis. Journal of Physical Oceanography, 33(4): 840-847.

It is hypothesized that tidal mixing may provide a "diffusivity'' mechanism for frontogenesis. It stems from the fact that tidal diffusivity varies in the opposite sense from the water depth, so the vertically integrated diffusivity may exhibit a minimum at midshelf, thus giving rise to a maximum in the property gradient-even in the absence of flow convergence. An analytical model assuming a tidal diffusivity dominated by shear dispersion is used to elucidate the mechanism, which shows additionally that the front is located at a water depth that is about twice the tidal frictional depth-a prediction not inconsistent with some observed fronts. The proposed frontogenesis is demonstrated by numerical calculations using the Princeton Ocean Model (POM), which show the emergence of a front from an initial field of uniform gradient after tides are switched on, and the diagnosis of the numerical solution and its parameter dependence has corroborated the analytical model. It is suggested moreover that this diffusivity mechanism may be extended to the wind-induced mixing to explain the shelfbreak front off of the northeastern United States.


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Perlwitz, J. and N. Harnik, 2003: Observational evidence of a stratospheric influence on the troposphere by planetary wave reflection. Journal of Climate, 16(18): 3011-3026.

Recent studies have pointed out the impact of the stratosphere on the troposphere by dynamic coupling. In the present paper, observational evidence for an effect of downward planetary wave reflection in the stratosphere on Northern Hemisphere tropospheric waves is given by combining statistical and dynamical diagnostics. A time-lagged singular value decomposition analysis is applied to daily tropospheric and stratospheric height fields recomposed for a single zonal wavenumber. A wave geometry diagnostic for wave propagation characteristics that separates the index of refraction into vertical and meridional components is used to diagnose the occurrence of reflecting surfaces. For zonal wavenumber 1, this study suggests that there is one characteristic configuration of the stratospheric jet that reflects waves back into the troposphere - when the polar night jet peaks in the high-latitude midstratosphere. This configuration is related to the formation of a reflecting surface for vertical propagation at around 5 hPa as a result of the vertical curvature of the zonal-mean wind and a clear meridional waveguide in the lower to middle stratosphere that channels the reflected wave activity to the high-latitude troposphere.


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Pollack, H. N., D. Y. Demezhko, A. D. Duchkov, I. V. Golovanova, S. P. Huang, V. A. Shchapov and J. E. Smerdon, 2003: Surface temperature trends in Russia over the past five centuries reconstructed from borehole temperatures. Journal of Geophysical Research-Solid Earth, 108(B4): doi:10.1029/2002JB002154.

We analyze borehole temperature logs from 101 sites in Russia and nearby areas to reconstruct the ground surface temperature history (GSTH) over the past five centuries. The data are drawn principally from three regions: the Urals, southwest Siberia, and northeast Siberia. We derive GSTHs for each region individually, and a composite "all-Russia" GSTH from the full ensemble of sites. The results show that over the past 500 years, the investigated areas have on average warmed similar to1 K, with more than half of the warming occurring in the 20th century alone, and 70-80% in the 19th and 20th centuries taken together. The 16th through 18th centuries in the Urals and southwest Siberia were on average 0.1-0.2 K cooler than at the beginning of the 19th century, but northeast Siberia was more moderate in the 16th through 19th centuries, relative to the present-day, than the Urals or southwest Siberia. A wide variety of instrumental, proxy, and indirect evidence support these geothermal results.


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Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. Journal of Geophysical Research-Atmospheres, 108(D14): doi:10.1029/2002JD002670.

We present the Met Office Hadley Centre's sea ice and sea surface temperature (SST) data set, HadISST1, and the nighttime marine air temperature (NMAT) data set, HadMAT1. HadISST1 replaces the global sea ice and sea surface temperature (GISST) data sets and is a unique combination of monthly globally complete fields of SST and sea ice concentration on a 1degrees latitude-longitude grid from 1871. The companion HadMAT1 runs monthly from 1856 on a 5degrees latitude-longitude grid and incorporates new corrections for the effect on NMAT of increasing deck (and hence measurement) heights. HadISST1 and HadMAT1 temperatures are reconstructed using a two-stage reduced-space optimal interpolation procedure, followed by superposition of quality-improved gridded observations onto the reconstructions to restore local detail. The sea ice fields are made more homogeneous by compensating satellite microwave-based sea ice concentrations for the impact of surface melt effects on retrievals in the Arctic and for algorithm deficiencies in the Antarctic and by making the historical in situ concentrations consistent with the satellite data. SSTs near sea ice are estimated using statistical relationships between SST and sea ice concentration. HadISST1 compares well with other published analyses, capturing trends in global, hemispheric, and regional SST well, containing SST fields with more uniform variance through time and better month-to-month persistence than those in GISST. HadMAT1 is more consistent with SST and with collocated land surface air temperatures than previous NMAT data sets.


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Robertson, R., A. Beckmann and H. Hellmer, 2003: M-2 tidal dynamics in the Ross Sea. Antarctic Science, 15(1): 41-46.

In certain regions of the Southern Ocean, tidal energy is believed to foster the mixing of different water masses, which eventually contribute to the formation of deep and bottom waters. The Ross Sea is one of the major ventilation sites of the global ocean abyss and a region of sparse tidal observations. We investigated M-2 tidal dynamics in the Ross Sea using a three-dimensional sigma coordinate model, the Regional Ocean Model System (ROMS). Realistic topography and hydrography from existing observational data were used with a single tidal constituent, the semi-diurnal M-2. The model fields faithfully reproduced the major features of the tidal circulation and had reasonable agreement with ten existing tidal elevation observations and forty-two existing tidal current measurements. The differences were attributed primarily to topographic errors. Internal tides were generated at the continental shelf/slope break and other areas of steep topography. Strong vertical shears in the horizontal velocities occurred under and at the edges of the Ross Ice Shelf and along the continental shelf/slope break. Estimates of lead formation based on divergence of baroclinic velocities were significantly higher than those based on barotrophic velocities, reaching over 10% at the continental shelf/slope break.


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Seager, R., N. Harnik, Y. Kushnir, W. Robinson and J. Miller(Nakamura), 2003: Mechanisms of hemispherically symmetric climate variability. Journal of Climate, 16(18): 2960-2978.

Inspired by paleoclimate evidence that much past climate change has been symmetric about the equator, the causes of hemispherically symmetric variability in the recent observational record are examined using the National Centers for Environmental Prediction - National Center for Atmospheric Research reanalysis dataset and numerical models. It was found that the dominant cause of hemispherically symmetric variability is the El Nino-Southern Oscillation. During an El Nino event the Tropics warm at all longitudes and the subtropical jets in both hemispheres strengthen on their equatorward flanks. Poleward of the tropical warming there are latitude belts of marked cooling, extending from the surface to the tropopause in both hemispheres, at all longitudes and in all seasons. The midlatitude cooling is caused by changes in the eddy-driven mean meridional circulation. Changes in the transient eddy momentum fluxes during an El Nino event force upper-tropospheric ascent in midlatitudes through a balance between the eddy fluxes and the Coriolis torque. The eddy-driven ascent causes anomalous adiabatic cooling, which is primarily balanced by anomalous diabatic heating.


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Seager, R., R. Murtugudde, N. H. Naik(Henderson), A. Clement, N. Gordon and J. Miller(Nakamura), 2003: Air-sea interaction and the seasonal cycle of the subtropical anticyclones. Journal of Climate, 16(12): 1948-1966.

The causes of the seasonal cycles of the subtropical anticyclones, and the associated zonal asymmetries of sea surface temperature (SST) across the subtropical oceans, are examined. In all basins the cool waters in the east and warm waters in the west are sustained by a mix of atmosphere and ocean processes. When the anticyclones are best developed, during local summer, subsidence and equatorward advection on the eastern flanks of the anticyclones cool SSTs, while poleward flow on the western flanks warms SSTs. During local winter the SST asymmetry across the subtropical North Atlantic and North Pacific is maintained by warm water advection in the western boundary currents that offsets the large extraction of heat by advection of cold, dry air of the continents and by transient eddies. In the Southern Hemisphere ocean processes are equally important in cooling the eastern oceans by upwelling and advection during local winter. Ocean dynamics are important in amplifying the SST asymmetry, as experiments with general circulation models show. This amplification has little impact on the seasonal cycle of the anticyclones in the Northern Hemisphere, strengthens the anticyclones in the Southern Hemisphere, and helps position the anticyclones over the eastern basins in both hemispheres. Experiments with an idealized model are used to suggest that the subtropical anticyclones arise fundamentally as a response to monsoonal heating over land but need further amplification to bring them up to observed strength. The amplification is provided by local air - sea interaction. The SST asymmetry, generated through local air - sea interaction by the weak anticyclones forced by heating over land, stabilizes the atmosphere to deep convection in the east and destabilizes it in the west. Convection spreads from the land regions to the adjacent regions of the western subtropical oceans, and the enhanced zonal asymmetry of atmospheric heating strengthens the subtropical anticyclones.


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Shaman, J., J. F. Day and M. Stieglitz, 2003: St. Louis encephalitis virus in wild birds during the 1990 South Florida epidemic: The importance of drought, wetting conditions, and the emergence of Culex nigripalpus (Diptera : Culicidae) to arboviral amplification and transmission. Journal of Medical Entomology, 40(4): 547-554.

We analyzed the prevalence of hemagglutination inhibition (HI) antibodies to St. Louis encephalitis (SLE) virus in wild birds during the 1990 SLE epidemic in Indian River County. The initial presence of SLE HI antibody was associated significantly with modeled drought 15 wk prior, wetting conditions 1 wk prior, and the emergence of the Florida SLE virus vector, Culex nigripalpus, 5 wk prior. Our findings indicated that three factors conspired to create the 1990 epidemic: (1) a large population of susceptible wild birds; (2) severe springtime drought, which facilitated amplification of the SLE virus among the Cx. nigrqpalpus and a portion of the wild bird population; and (3) continued rainfall and wetting of the land surface in the summer and early fall, which sustained a large, bost-seeking Cx. nigripalpus population. The continued biting and reproductive activity of Cx. nigripalpus maintained epizootic transmission throughout the summer and early fall in Indian River County. The high level of SLE virus amplification resulted in spillover transmission to humans. We hypothesize that without the continued reproductive activity of the vector mosquito, brought about by excessive summer and fall wetness, the unprecedented SLE virus amplification and consequent transmission to humans would not have been realized in 1990.


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Shaman, J., M. Stieglitz, S. Zebiak and M. A. Cane, 2003: A local forecast of land surface wetness conditions derived from seasonal climate predictions. Journal of Hydrometeorology, 4(3): 611-626.

An ensemble local hydrologic forecast derived from the seasonal forecasts of the International Research Institute for Climate Prediction (IRI) is presented. Three-month seasonal forecasts were used to resample historical meteorological conditions and generate ensemble forcing datasets for a TOPMODEL-based hydrology model. Eleven retrospective forecasts were run at Florida and New York sites. Forecast skill was assessed for mean area modeled water table depth (WTD) and compared with WTD simulated with observed data. Hydrology model forecast skill was evident at the Florida site. Persistence of initial hydrologic conditions and local skill of the IRI seasonal forecast contributed to this local hydrologic forecast skill. At the New York site, there was no persistence of initial hydrologic conditions and local skill of the IRI seasonal forecast was poor; these factors precluded local hydrologic forecast skill at this site.


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Smerdon, J. E., H. N. Pollack, J. W. Enz and M. J. Lewis, 2003: Conduction-dominated heat transport of the annual temperature signal in soil. Journal of Geophysical Research-Solid Earth, 108(B9): doi:10.1029/2002JB002351.

[1] Conductive heat transport of temperature signals into the subsurface is a central assumption of ground surface temperature (GST) reconstructions derived from present-day temperatures in deep boreholes. Here we test this assumption and its implications for annual relationships between GST and surface air temperature (SAT) by analyzing two decades of shallow soil temperature (0.01 - 11.7 m) and SAT time series measured at Fargo, North Dakota. We spectrally decompose each of these temperature time series to determine the amplitude and phase of the annual signal at each depth. Conductive heat transport of a harmonic temperature signal in a homogeneous medium is characterized theoretically by exponential amplitude attenuation and linear phase shift with depth. We show that transport of the annual signal in the soil at Fargo follows these theoretical characterizations of conduction closely: the depth dependence of both the natural logarithm of the amplitude and the phase shift are highly linear. Interval wave velocities and thermal diffusivities calculated as functions of depth suggest a diffusivity gradient in the upper meter of the soil. We estimate the annual signal at the ground surface by extrapolating amplitude and phase shift regression lines upward to the surface. We compare this estimate of the annual signal at the ground surface to the annual signal contained in the SAT and show the ground surface signal to be attenuated similar to 20% and negligibly phase shifted relative to the SAT.


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Stieglitz, M., S. J. Dery, V. E. Romanovsky and T. E. Osterkamp, 2003: The role of snow cover in the warming of arctic permafrost. Geophysical Research Letters, 30(13): doi:10.1029/2003GL017337,.

[1] Air temperatures at high latitudes are expected to rise significantly as anthropogenic carbon builds up in the atmosphere. There is concern that warming of the ground in permafrost regions will result in additional release of carbon to the atmosphere. Recent emphasis has thus been on predicting the magnitude and spatial distribution of future warming at high latitudes. Modeling results show that changes in below ground temperatures can be influenced as much by temporal variations of snow cover as by changes in the near-surface air temperature. The recent (1983-1998) changes in permafrost temperatures on the North Slope of Alaska are consistent with decadal scale variability in snow cover. The implication of these results is that a better understanding of how winter precipitation patterns at high latitudes will change over the coming decades is needed to comprehend evolving permafrost temperatures.


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Thurnherr, A. M. and K. G. Speer, 2003: Boundary mixing and topographic blocking on the Mid-Atlantic Ridge in the South Atlantic. Journal of Physical Oceanography, 33(4): 848-862.

It is commonly observed in hydrographic sections crossing midocean ridges that the isopycnals on the ridge flanks slope downward toward the crests. Although the observed vertical scales of isopycnal dipping are not consistent with steady diffusive boundary layers on slopes, the cross-flank density gradients can nevertheless be caused by diapycnal mixing acting on timescales of several years. The corresponding pressure gradients are usually inferred to be associated with cyclonic along-flank flows. Recent observations of southward flow along the highly corrugated western flank of the Mid-Atlantic Ridge near 20degreesS are inconsistent with this conceptual picture, however. Data from seven zonal cross-ridge sections and from four meridional along-ridge sections were used to analyze the hydrography on the flanks of the Mid-Atlantic Ridge between 2degreesN and 30degreesS. The majority of the hydrographic stations were occupied over deep cross-flank canyons, which extend over a total length of; 90 000 km in the tropical and subtropical South Atlantic alone. The dipping of the isopycnal surfaces on the western ridge flank in the Brazil Basin is largely restricted to the canyons, where flow along the flank is topographically blocked. The magnitudes of the blocked apparent along-ridge transports are typically of order 1 Sv (1 Sv = 10(6) m(3) s(-1)) with values as high as 3 Sv, implying important consequences for circulation studies with both forward and inverse models. In the southern Brazil Basin the horizontal density gradients immediately above the blocking topography are reversed-that is, the densities increase toward the crest of the Mid-Atlantic Ridge, consistent with observations of southward flow along the flank. On the eastern flank in the Angola Basin there is a layer of crestward-increasing densities as well, but there it lies well above the ridge topography. Numerical solutions of the buoyancy equation indicate that the observed cross-flank density gradients of both signs are consistent with bottom-intensified diapycnal mixing, which causes a vertical buoyancy-flux dipole. Boundary mixing on slopes can therefore give rise to anticyclonic, as well as cyclonic, along-slope flows. The observed horizontal temperature and salinity gradients near the Mid-Atlantic Ridge in the South Atlantic cannot be accounted for by diapycnal mixing alone, on the other hand. The distributions of these properties are therefore largely determined by isopycnal processes.


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Wajsowicz, R. C., A. L. Gordon, A. Ffield and R. D. Susanto, 2003: Estimating transport in Makassar Strait. Deep-Sea Research Part II-Topical Studies in Oceanography, 50(12-13): 2163-2181.

Monthly averaged current meter data from two moorings in Labani Channel are examined, and a method, based on fitting normal modes, is developed to estimate the transport through Makassar Strait. The data span a depth range from about 210 to 1500 m and a time period from November 1996 to July 1998. They show monthly averaged southward currents in excess of 50 cm s(-1) at 250 m, and episodes ranging from 1-6 months of 5-10 cm s(-1) northward flow below 600 m. Estimates of the along-channel flow above and below the data record are made by fitting normal vertical modes, derived from climatological buoyancy frequency profiles, to the data. Tests of the fitting method show that the depth-averaged value is recovered well for profiles truncated between 200 and 250 m, but that the baroclinic structure cannot be recovered if more than the upper similar to 50 m of data are missing. However, for some almost full-depth acoustic Doppler profiles taken in Makassar Strait, the reconstructed flow averaged over the upper 250 m is typically found to lie within the bounds provided by the method. The estimated mean depth-integrated transport for 1997 is 6.4 Sv southwards with upper and lower bounds of 16.0 and 4.7 Sv respectively. Over the upper 250 m, the estimated mean transport for 1997 is 2.0 Sv southwards with upper and lower bounds of 9.7 and 0.8 Sv, respectively. The upper (lower) bounds are given by a normal mode reconstruction in which the first (third) baroclinic mode dominates the profile for much of the year; for the best estimate, the second baroclinic mode dominates the profiles through most of the year. The estimated mean net transport range for 1997 encompasses the earlier range published by Gordon et al. (Geophys. Res. Lett. 26 (1999) 3325), where empirical formulae were used to extrapolate the current profiles to the sea surface. The normal-mode reconstruction of the flow, temperature data from T-pods on the western Labani Channel mooring, and temperature and zonal wind data from the TAO moorings in the equatorial Pacific Ocean, provide a consistent description of cool, upwelling (warm, downwelling) baroclinic Rossby waves being scattered into the Indonesian archipelago as the equatorial zonal winds collapse (intensify) at the onset of El Ni (n) over tildeo (La Ni (n) over tildea). (C) 2003 Elsevier Science Ltd. All rights reserved.


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Zappa, C. J., P. A. Raymond, E. A. Terray and W. R. McGillis, 2003: Variation in surface turbulence and the gas transfer velocity over a tidal cycle in a macro-tidal estuary. Estuaries, 26(6): 1401-1415.

The gradient flux technique, which measures the gas transfer velocity (k), and new observational techniques that probe turbulence in the aqueous surface boundary layers were conducted over a tidal cycle in the Plum Island Sound, Massachusetts. Efforts were aimed at testing new methods in an estuarine system and to determine if turbulence created by tidal velocity can be responsible for the short-term variabitity in k. Measurements were made during a low wind day, at a site with tidal excursions of 2.7 m and a range in tidal velocity of nearly 1 m s(-1). Estimates of k using the gradient flux technique were made simultaneously with the Controlled Flux Technique (CFT), infrared imagery, and high-resolution turbulence measurements, which measure the surface renewal rate, turbulent scales, and the turbulent dissipation rate, respectively. All measurements were conducted from a small mobile catamaran that minimizes air- and water-side flow distortions. Infrared imagery showed considerable variability in the turbulent scales that affect air-water gas exchange. These measurements were consistent with variation in the surface renewal rate (range 0.02 to 2 s(-1)), the turbulent dissipation rate (range 10(-7) to 10(-5) W kg(-1)), and k (range 2.2 to 12.0 cm hr(-1)). During this low wind day, all variables were shown to correlate with tidal speed. Taken collectively our results indicate the promise of these methods for determining short-term variability in gas transfer and near surface turbulence in estuaries and demonstrate that turbulent transport associated with tidal velocity is a potentially important factor with respect to gas exchange in coastal systems.


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The database was updated today.

Maintained by: Virginia DiBlasi, Lamont-Doherty Earth Observatory of Columbia University