Quality monitoring of UK network radars using synthesised observations from the Met Office Unified Model

The Met Office radar processing system delivers quality-controlled radar reflectivities to NWP. Quality information and radar reflectivity data are then passed to the Observation Processing System (OPS) where synthetic observations are calculated using model fields interpolated at the exact observation locations. Long-term statistical comparison between synthetic and real observations has the advantage of identifying individual radar calibration problems through relative comparisons with other radars. The effectiveness of the forward modelling of the reflectivity can also be evaluated through absolute statistical comparisons. Presented here is an analysis of statistical information derived from the quality monitoring system. Included is a description of the contribution made to the radar signal bias with range as a result of the combined effects of the bright band, attenuation by rain and clouds and beam broadening. The results are used to demonstrate that the atmospheric gaseous attenuation makes a significant contribution to the overall range bias, and it is therefore beneficial to account for this within the radar site processing.