Objective Analysis and Assimilation of Observational Data from FGGE

An objective analysis scheme developed at the Goddard Laboratory for Atmospheric Sciences (GLAS) to assimilate meteorological data is described. Wind, geopotential height, and relative humidity are analyzed on mandatory pressure levels. Surface pressure and temperature are reduced to sea level and analyzed there. The objective analysis procedure is of the successive correction type, but modified to account for variable data density and quality. A sample analysis is presented for 1200 GMT 19 January 1979 and shows good agreement with the one produced by the European Centre for Medium Range Weather Forecasts (ECMWF). The present analysis/forecast system demonstrates reasonable forecast skill over the Northern Hemisphere for an ensemble of five-day integrations during the First Special Observing Period (SOP-1) of the First GARP (Global Atmospheric Research Program) Global Experiment (FGGE). The vertical motion field shows excellent agreement with the large-scale synoptic pattern for the 1200 GMT 19 January case. The mean meridional circulation depicted in the FGGE analysis is in close agreement with observational estimates.