Validation of the Global Precipitation Measurement Mission Core Observatory Over Great Britain and Ireland

This study compares the instantaneous surface rain rate estimates over Great Britain and Ireland (GBI) from the spaceborne dual-frequency precipitation radar (DPR) and the GPM microwave imager (GMI) on board the GPM Core Observatory (GPM-CO) to estimates from the ground-based United Kingdom Meteorological Office's ground-radar network. In particular, the version-5, level-2 DPR and DPR-GMI (CMB) combined products (5 km resolution) and the Radarnet 4 radar composite product (1 km resolution) are used for the three year study (May 2014 - April 2017). Products are collocated both temporally and spatially, and subject to quality control, prior to the comparison where the Radarnet product is considered to be the “ground truth”. The GPM products are found to underestimate the surface rain rates detected by the Radarnet product from a sample of 575512 collocated 5 km data. The CMB product (bias -2% and correlation 0.49) performs better in comparison to the DPR product (bias -17% and correlation 0.42). Large standard deviations of around 132% suggest that the results are highly variable.