Evaluation of high-resolution satellite precipitation products with ground-based measurements over Europe

Sammanfattning: Determining water quantity of precipitation, spatially and temporally is fundamental for weather forecasting, applications in hydrology and meteorology, climate science and for agriculture and industry. Only satellite measurements from space are able to perform large-scale measurements covering both, ocean and land. In order to prove the reliability of the satellite data for application, but also to develop and improve the satellite retrievals of precipitation data, the satellite products need to be evaluated with reliable ground-based measurements. The high-resolution satellite data that this study is based on, was provided at a global scale by the satellite network Global Precipitation Measurement (GPM) that builds an international constellation of research and operational satellites. Previous evaluation of GPM dataset have shown error characteristics, related to topography, climate and latitude, that are potentially linking back to the sensor input, such as the calibrated passive microwave estimates (PMW), being a fundamental source for the final product. Evaluating the PMW estimates over a large region can improve the understanding of the error sources in the combined final GPM product. This study evaluated the calibrated PMW estimates (the primary foundation of the GPM IMERG final product) over Europe for the period from March 2014 to the end of December 2019 by using the blended gauge data from, provided by European Climate Assessment and Dataset (ECA&D), as reference. The data was evaluated seasonally, conducting different error indices to compare the satellite product with the gauge data and linking it to topography, climate and latitude. The results showed clear relationships between PMW data accuracy with elevation and climate zones in Europe, that can be linked to difficulties for PMW sensors to measure e.g. frozen precipitation, observe from a cold background, or when convection occurs in warmer climates. Also, for the relation to latitude, a worse performance with latitude was found, however only in winter, when frozen precipitation is likely at higher latitudes. Correcting those input sources, based on accuracy assessments, such as it was assessed by this study, can be meaningful for further improving GPM product.