Mesoscale initialisation using advanced sounder data

Abstract

There is increasing availability of continuous, high resolution observations from space-based platforms, for example, cloud and water vapour motion vectors, Advanced TOVS data and scatterometer wind fields, as well as increasing availability of continuous surface observations such as radar and profiler data. In addition, there will be, in the near future, an increase in the density of these data as instruments such as the Atmospheric InfraRed Sounder (AIRS) come into service. Full exploitation of this increased data base is expected to be attained through the use of modern data assimilation techniques such as 3- and 4-dimensional variational assimilation. Here, we briefly review the 4-D variational (4-D Var.) data assimilation system, initially developed by Bennet et al. (1993, 1995, 1996) and recently extended to include the mesoscale assimilation of wind, temperature and moisture data over a limited area (Le Marshall et al. 1999, Leslie et al. 1998). We describe the assimilation methodology and the summarise initial results obtained by applying this high resolution system to mesoscale data from the NAST-I (NPOESS Advanced Sounder Testbed - Infrared) advanced sounding instrument.