A Comparison of Divergent Winds from the National Meteorological Center and the European Centre for Medium Range Weather Forecasts Global Analyses for 1980–1986

Abstract

A comparison is made of the divergent wind analyses of the National Meteorological Center (NMC) and those of the ECMWF/WMO dataset produced by the European Centre for Medium Range Weather Forecasts (ECMWF). Using a reliability criterion based on the degree of correlation between month-long time series of daily values, the utility of the analyses is assessed over the globe on seven pressure levels from 100 to 1000 mb for all Januarys and Julys between 1980 and 1986. The results indicate that from January 1983 onward, the analyses for the winter hemisphere midlatitudes (≈20°?70°) and for the summer hemisphere midlatitudes (≈35°?70°) should be considered reliable except in midtropospheric levels where the divergence is weak. The tropical (between about 20° latitude of the winter hemisphere and 35° latitude of the summer hemisphere) analyses are especially poor and fall far short of satisfying the reliability criterion.