AN ASSIMILATED DATASET FOR EARTH-SCIENCE APPLICATIONS

The Data Assimilation Office at NASA's Goddard Space Flight Center is currently producing a multiyear gridded global atmospheric dataset for use in climate research, including tropospheric chemistry application s. The data, which are being made available to the scientific communit y, are well suited for climate research since they are produced by a f ixed assimilation system designed to minimize the spin up in the hydro logical cycle. By using a nonvarying system, the variability due to al gorithm change is eliminated and geophysical variability can be more c onfidently isolated. The analysis incorporates rawinsonde reports, sat ellite retrievals of geopotential thickness, cloud-motion winds, and a ircraft, ship, and rocketsonde reports. At the lower boundary, the ass imilating atmospheric general circulation model is constrained by the observed sea surface temperature and soil moisture derived from observ ed surface air temperature and precipitation fields. The available out put data include all prognostic variables and a large number of diagno stic quantities such as heating rates, precipitation, surface fluxes, cloud fraction, and the height of the planetary boundary layer. These variables were chosen to assure a complete budget of the energy and mo isture cycles. The assimilated data should also be useful for estimati ng transport by cumulus processes. The analysis increments (observatio n minus first guess) and the estimated analysis errors are provided to help the user assess the quality of the data. All quantities are made available every 6 h at the full resolution of the assimilating genera l circulation model. Selected surface quantities are made available ev ery 3 h.