Observation operator and observation processing for cloud radar. Support-to-Science-Element (STSE) Study EarthCARE Assimilation

Title
Observation operator and observation processing for cloud radar. Support-to-Science-Element (STSE) Study EarthCARE Assimilation
Report
Date Published
01/2014
Series/Collection
WP-1100 Report: ESA ESTEC Contract AO/I-6441/10/NL/CB
Author
S. Di Michele, 
Edouard Martins, 
AbstractThis report summarizes the work done to prepare for the inclusion of the EarthCARE radar data in the ECMWF monitoring/assimilation system using CloudSat observations as testing data. The first part of the study describes the refinements brought to the radar forward operator. Improvements to the definition of the optical properties of frozen precipitation has led to a better agreement between simulated and CloudSat reflectvities. The impact of multiple scattering on the radar signal has been also investigated. Simulations show that this phenomenon affects all precipitation regimes, degrading the signal in conditions of heavy precipitation. The second part of the study focuses on the characterization of the observation errors, needed for data assimilation. Uncertainties due to the observation operator have been estimated perturbating some of the microphysical assumptions there made. In case of space-borne radar observations as the ones from CloudSat/EarthCARE, an important component of the observation error is the representativity one. In this work a flow-dependent estimate has been implemented following a previously-developed statistical approach. The final part of the study describes the quality control and bias correction schemes developed in order to have departures between CloudSat observations and model first guess suitable for assimilation. ESA