Current status of the assimilation of radar reflectivity data at the Met Office

The processing of the radar data has been upgraded to deliver quality controlled reflectivities to the NWP observation processing system (OPS); Quality flags are produced and signal-to-noise ratio is used to quantify reflectivity random errors.

In the OPS, an observation operator for reflectivities has been implemented; various options have been considered to account for attenuation, beam bending and partial beam blockage; synthetic observations are calculated using model fields interpolated to the exact observation location. The differences between raw observations and synthetic observations are superobbed to the model grid. Monitoring of both the high resolution observations and the superobbed observations has been setup to derive long term O-B bias and standard deviation. A standalone variational retrieval has been developed to derive pseudo-profiles of temperature and humidity from volume scan reflectivities. The radar returned power (ie that includes background noise and the attenuation) is used in a 2D-Var scheme(height/range for given azimuth) based on simple incremental approach to retrieve temperature and humidity profiles on model levels. The assimilation of the retrieved temperature and humidity pseudo profiles is being tested in the 1.5 km UM using a 3D-Var hourly cycle.

An overview of our current setup will be given and initial results from assimilation experiments will be presented and discussed.