Scatterometer and reanalysis wind products over the western tropical Indian Ocean (original) (raw)
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Journal of Geophysical Research, 1986
We present instantaneous and 15-day time-averaged fields of surface wind, wind stress, curl of the wind stress, and wind divergence. These fields are derived from the Goddard Laboratory for Atmospheres four-dimensional analysis/forecast cycle, for the period September 6-20, 1978, using conventional data, satellite temperature soundings, cloud-track winds, and subjectively dealiased Seasat scatterometer winds.
Sensitivity of the Indian Ocean circulation to surface wind stress
2008
There is a lot of debate on the responses of Antarctic Circumpolar Current (ACC) in relations to changes in Southern Hemisphere winds and how the momentum input by the surface wind stress can be transferred down to the ocean floor. An σ coordinate Ocean General Circulation model was used in the present study. The major circulations in the Southern as well as tropical Indian Ocean have been discussed. The sensitivity of model with respect to wind stress forcing has been performed by using the surface wind stress climatological data of Hellerman and daSilva for the Indian Ocean up to 60ºS. It has been found that the response of zonal wind stress over tropical Indian Ocean north of 5ºS was large. The response of change in surface wind stress was negligible in the Southern Indian Ocean.
Validation of different global data sets for sea surface wind-stress
International Journal of Remote Sensing, 2020
Different surface wind-stress products over the global ocean were validated by comparing with in-situ measurements from moored buoys, and by inter-comparing among them. The products are ones constructed from satellite observations by microwave scatterometers and radiometers, and reanalysed ones by data assimilation and numerical models. Comparisons with buoy measurements revealed that the Cross-Calibrated Multi-Platform Version 2 (CCMP v2.0) has the lowest positive bias, the smallest root mean square error (RMSE) and the largest correlation coefficient in this intercomparison, meaning that the CCMP v2.0 gives the best performance. Inter-comparisons among the different wind-stress products exhibited that the meridional wind-stress data of the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) are not different in the subtropical region from those of other ones, and zonal and meridional wind-stress data of the National Centre for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) have relatively low values in the westerly region. In the zonal-spectral analysis, we found that the zonal wind-stress/wind-vector data from the Institut Français de Recherche pour la Recherche et l'Exploitation de la Mer (IFREMER) have short wave-like oscillations. Thus, the surface wind and windstress data in IFREMER products have been well affected by spatial resolution of background data used in their gridding procedure. We also investigated the spatial characteristics of wind-stress curl fields for the different data sets, and found that there are differences between the CCMP v2.0 and Japanese Ocean Flux Data sets with Use of Remote Sensing Observations Version 3 (J-OFURO3) which are characterized by spike-like features in the equatorial Pacific where there are the Tropical Atmosphere Ocean and the TRIangle Trans-Ocean buoy Network (TAO/TRITON) buoys. These features were spatially correlated with buoy locations, which suggests that the reliability of the CCMP v2.0 products is governed by buoy locations in this region.
Monthly Charts of Surface Wind Stress Curl Over the Indian Ocean
Monthly Weather Review, 1970
The surface wind stress curl is the forcing function in the equations of vertically integrated water transport of wind-driven ocean currents. Hence, i t has become a basic quantity in theoretical oceanography. As the time dependence of all important surface quantities in the Indian Ocean is stronger than in other oceans, it is valuable to look particularly a t the time variation in this region. This study presents monthly charts of the wind stress curl a t the surface of the Indian Ocean from its land boundaries up to 50" S. and from 20' E. to 116' E. Basic data were the monthly surface maps of the Koninklijk Nederlands Meteorologisch Instituut, derived from ship observations and given as 2" square means of the surface wind. The processing of the data is described in detail. I n particular, small-scale fluctuations arc objectively filtered out. While earlier compilations are usually on a coarser grid (seasonal and 5" square averages), the present data have a refined time and space resolution. Therefore, they allow onc to study more detailed structures. In particular, the charts show that the curl pattern in the Indian Ocean is not independent of longitude.
Wind stress and near-surface shear in the equatorial Atlantic Ocean
Geophysical Research Letters, 2014
The upper ocean response to wind stress is examined using 8 months of unique near-surface moored velocity, temperature, and salinity data at 0°N, 23°W in the equatorial Atlantic. The effects of wind stress and shear on the time-varying eddy viscosity are inferred using the surface shear-stress boundary condition. Parameterizations of eddy viscosity as a function of wind stress and shear versus wind stress alone are then examined. In principle, eddy viscosity should be proportional to the inverse shear, but how it is represented implicitly or explicitly can affect estimates of the near-surface flow field. This result may explain some discrepancies that have arisen from using parameterizations based only on wind stress to characterize the effects of turbulent momentum mixing.
Wind Stress Drag Coefficient over the Global Ocean*
Journal of Climate, 2007
Interannual and climatological variations of wind stress drag coefficient (CD) are examined over the global ocean from 1998 to 2004. Here CD is calculated using high temporal resolution (3- and 6-hourly) surface atmospheric variables from two datasets: 1) the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and 2) the Navy Operational Global Atmospheric Prediction System (NOGAPS). The stability-dependent CD algorithm applied to both datasets gives almost identical values over most of the global ocean, confirming the validity of results. Overall, major findings of this paper are as follows: 1) the CD value can change significantly (e.g., >50%) on 12-hourly time scales around the Kuroshio and Gulf Stream current systems; 2) there is strong seasonal variability in CD, but there is not much interannual change in the spatial variability for a given month; 3) a global mean CD ≈ 1.25 × 10−3 is found in all months, while CD ≥ 1.5 × 10−3 is prevalent o...
Sensitivity of the tropical Atlantic circulation to specification of wind stress climatology
Journal of Geophysical Research, 1995
This study examines the sensitivity of a simulation of the tropical Atlantic circulation to the choice of climatological wind stress forcing. Three climatological wind stress data sets, representing different classes of data products, are used to drive a high-resolution general circulation model of the Atlantic Ocean. One set is from historical surface marine datasets compiled by Hellerman and Rosenstein. The second climatology is based on surface wind analyses from the European Centre for Medium Range Weather Forecasts. The last climatology is derived from an integration of the National Center for Atmospheric Research Community Climate Model, version 2, at T42 resolution (CCM2). The analysis of the model sensitivity to these different wind stress climatologies focuses on the mean seasonal cycle and low order statistics of the simulated upper ocean circulation in the tropics and its comparison with observations. In the North Equatorial Countercurrent (NECC) the three simulations agree with each other and with observations reasonably well. The differences that do exist in the simulation of the NECC are primarily in smaller-meridional-scale features and in the phase of the onset and decay. There are much larger differences among the simulations near the equator. Most of these differences in the equatorial circulation are attributable to differences in the cross-equatorial meridional wind stress. The ECMWF climatology has relatively weak meridional stress and correspondingly weak equatorial upwelling. The CCM2 climatology has unrealistically large meridional stress and equatorial upwelling.