A Test of the ECMWF Model in Tropical Synoptic-Scale Diagnosis

Abstract

The originally disseminated ECMWF-FGGE analyses for January and February 1979 are used to study the model performance in the deep tropics. Vertical velocities representing both the normal-mode initialized and uninitialized synoptic-scale flow are compared to directly observed IR radiance from the TIROS-N polar orbiting satellite. This comparison, based on the correlation between cloudiness and vertical motion, is made in the Pacific sector for composites of 1) the intertropical convergence zone, 2) the South Pacific convergence zone, and 3) Northern Hemisphere tropical intrusions. When compared to the uninitialized version, initialization diminishes the magnitude of diagnosed vertical motions in the tropics and Southern Hemisphere by a factor of 2 to 4. For synoptic-scale events away from the equator, especially at upper levels, the patterns of vertical motion are quite similar to each other and correlate moderately well with the radiance observations. Poor correlations in the deep tropics indicate that the original ECMWF-FGGE analyses within 10° of the equator are deficient on the synoptic scale and should be interpreted with caution in this domain.