Monitoring the Performance of the ECMWF Operational Analysis Using the Enhanced TOGA COARE Observational Network

Abstract

An enhanced atmospheric monitoring effort has been set up during the Intensive Observation Period (IOP) of the Coupled Ocean-Atmosphere Response Experiment (COARE), devoted to better describe the ocean-atmosphere 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 November 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 differences between observations and analyses show a systematic underestimation 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 ≈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 pronounced, showing that the biases are partly induced by the model parameterizations. Moreover, it is shown that the analysis is very close to the first 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 distributed.