Evaluation of decadal hindcasts by application of a satellite simulator for SSM/I & SSMIS

A satellite simulator for the Special Sensor Microwave Imager (SSM/I) and for the Special Sensor Microwave Imager and Sounder (SSMIS) is developed and applied to decadal hindcast simulations performed within the MiKlip project (http://fona-miklip.de, funded by the Federal Ministry of Education and Research in Germany). The aim is to evaluate the climatological and predictive skill of the hindcasts focusing on water cycle components. Classical evaluation approaches commonly focus on geophysical parameters such as temperature, precipitation or wind speed using observational datasets and reanalysis as reference. The employment of the satellite simulator enables an evaluation in the instrument's parameter and thereby reduces uncertainties on the reference side. The simulators are developed utilizing the CFMIP Observation Simulator Package (COSP, http://cfmip.metoffice.com/COSP.html). On the reference side the SSM/I & SSMIS Fundamental Climate Data Record (FCDR) provided by the CM SAF (DOI: 10.5676/EUM_SAF_CM/FCDR_MWI/V003) is used which constitutes a quality controlled, recalibrated and intercalibrated record of brightness temperatures for the period from 1978 to 2015. Simulated brightness temperatures for selected channels which are sensitive to either water vapor content (22 GHz) or hydrometeor content (85 GHz, vertical minus horizontal polarization) as an indicator for precipitation are used. For lead year 1 analysis of variance (ANOVA) reveals potential predictability for large parts of the tropical ocean areas for both water vapor and precipitation related channels. Furthermore, the Conditional Ranked Probability Skill Score (CRPSS) indicates predictive skill for large parts of the tropical/sub-tropical Pacific, parts of the tropical/sub-tropical Atlantic and the equatorial Indian Ocean. For lead years 2-3 ANOVA still indicates potential predictability for equatorial ocean areas. Moreover, CRPSS indicates predictive skill for parts of the tropical/subtropical ocean areas. These results suggest that the hindcasts show skill even beyond lead year 1 when comparing against climatology as a reference forecast.