Use of Cloud-Affected Microwave Radiances at the Met Office and Interaction with Variational Data Assimilation

In this presentation we will summarise the recent work performed to improve our use of microwave sounding data as we move towards the ultimate goal of using observations in all scenes, including those with significant liquid and ice cloud effects. Currently our focus is on the AMSUA and MHS instruments. We will review improvements to the forward modelling of radiances from these instruments in both our preprocessing and Variational data assimilation systems, including updates to the RTTOV-12 radiative transfer model. The use of 1D Variational assimilation within our pre-processing step to diagnose liquid and ice cloud water path will also be discussed.

Operationally at the Met Office the 4D Variational data assimilation system uses a single outer loop of the full non linear NWP forecast model to provide model fields for linearisation and observation operators. Using outer loop cycling as part of the assimilation has the potential to extend the forecast benefit of cloudy radiances, for instance into the wind field. We will present initial results looking at the interaction of cloudy radiances within this framework.

Finally future plans to extend this work to other sensors and missions will be discussed.