Improved use of AMSU-B data in the UK Met Office regional models

Regional Numerical Weather Prediction (NWP) models provide enhanced detail for forecast quantities such as cloud cover, visibility and rainfall. Previous work at the Met Office has shown that improving the humidity analysis through the assimilation of AMSU radiances improves the accuracy of these quantities. This paper highlights several new developments in the assimilation of AMSU-B radiances for regional models, including the use of data at the full resolution of 16km and in the selection of which channels to use in the analysis. The channel selection method uses the cloud liquid water in each profile estimated from a 1D-Var scheme. Comparisons are presented from 3D-Var runs which show that the size of the moisture increments in the boundary layer due to AMSU-B observations is similar to those from radiosondes.