Chapter 23 - Radar data assimilation in numerical weather prediction models

Abstract

The numerical weather prediction (NWP) center assimilates a variety of observation data to improve the accuracy of initial conditions. Radar data are also assimilated at NWP centers to improve the accuracy of forecasts. This chapter focuses on data assimilation using the variational method and briefly introduces the current status of radar data assimilation at the operational NWP centers. First, we show how to treatment the non-Gaussian distribution of precipitation observations in the radar data assimilation method. Next, an indirect assimilation method based on Bayesian theory is described. In this method, radar observations are first converted to nonradar meteorological elements. Then, the converted values are assimilated as conventional observations. Finally, the current status of the direct assimilation method of radar observations using the variational method at the NWP center and future issues are described.