MONITORING THE PERFORMANCE OF THE ECMWF OPERATIONAL ANALYSIS USING THE ENHANCED TOGA COARE OBSERVATIONAL NETWORK

An enhanced atmospheric monitoring effort has been set up during the I ntensive Observation Period (IOP) of the Coupled Ocean-Atmosphere Resp onse Experiment (COARE), devoted to better describe the ocean-atmosphe re system of the western Pacific near-equatorial warm pool. The field phase of COARE was one component of the international Tropical Oceans and Global Atmosphere (TOGA) program, and the IOP took place from 1 No vember 1992 through 28 February 1993. The authors compare the European Centre for Medium-Range Weather Forecasts operational analysis to the radiosonde measurements at three sites (with four soundings per day) deployed in the vicinity of the equator. The statistics of the differe nces between observations and analyses show a systematic underestimati on of the analyzed wind speed, close to 1 m s(-1), reaching 2 m s(-1) at the easterly jet level, and an overestimation of approximate to 1 m s(-1) at 1000 hPa. Analyzed humidity is too dry in the midtroposphere and too moist in the low troposphere. Analyzed temperature exhibits a more complicated behavior, but the high troposphere is generally too cold. The statistics of the differences between observations and first -guess temperature fields show similar features but are more pronounce d, showing that the biases are partly induced by the model parameteriz ations. Moreover, it is shown that the analysis is very close to the f irst guess for 0600 and 1800 UTC due to the loss of observations over the Global Transmission System. Hence, a reanalysis with all the data is strongly suggested.