Comparison of surface wind stress characteristics over the Tropical Atlantic (10°N–40°S) in fields derived from the UWM/COADS, NCEP/NCAR and QuikSCAT datasets

A comparison of monthly wind stress derived from winds of NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis and UWM/COADS (The University of Wisconsin-Milwaukee/Comprehensive Ocean-Atmosphere Data Set) dataset (1950–1993), and of NCEP/NCAR reanalysis and satellite-based QuikSCAT dataset (2000–2006), is made over the South Atlantic (10°N–40°S). On a mean seasonal scale, the comparison shows that these three wind stress datasets have qualitatively similar patterns. Quantitatively, in general, from about the equator to 20°S in the mid-Atlantic the wind stress values are stronger in NCEP/NCAR data than those in UWM/COADS data. On the other hand, in the Intertropical Convergence Zone (ITCZ) area the wind stress values in NCEP/NCAR data are slightly weaker than those in UWM/COADS data. In the South Atlantic, between 20° S–40°S, the QuikSCAT dataset presents complex circulation structures which are not present in NCEP/NCAR and UWM/COADS data. The wind stress is used in a numerical ocean model to simulate ocean currents, which are compared to a drifting-buoy observed climatology. The modeled South Equatorial Current agrees better with observations between March–May and June–August. Between December–February, the South Equatorial Current from UWM/COADS and QuikSCAT experiments is stronger and more developed than that from NCEP/NCAR experiment. The Brazil Current, in turn, is better represented in the QuikSCAT experiment. Comparison of the annual migration of ITCZ at 20° and 30°W in UWM/COADS and NCEP/NCAR data sources show that the southernmost position of ITCZ at 30°W in February, March and April coincides with the rainy season in NE Brazil, while the northernmost position of ITCZ at 20°W in August coincides with the maximum rainfall of Northwest Africa.