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. CloudSat observations are used in combination with collocated European Centrefor Medium-Range Weather Forecasts (ECMWF) reanalysis to simulate space-borneW-band Doppler observations from slant-looking radars. The simulator alsoincludes cross-polarization effects which are relevant if the Dopplervelocities are derived from polarization diversity pulse pair correlation. Aspecific conically scanning radar configuration (WIVERN), recentlyproposed to the ESA-Earth Explorer 10 call that aims to provide globalin-cloud winds for data assimilation, is analysed in detail in this study. One hundred granules of CloudSat data are exploited to investigate the impacton Doppler velocity estimates from three specific effects: (1) non-uniformbeam filling, (2) wind shear and (3) crosstalk between orthogonalpolarization channels induced by hydrometeors and surface targets. Errorsassociated with non-uniform beam filling constitute the most important sourceof error and can account for almost 1 m s −1 standard deviation, but thiscan be reduced effectively to less than 0.5 m s −1 by adoptingcorrections based on estimates of vertical reflectivity gradients.Wind-shear-induced errors are generally much smaller ( ∼0.2  m s −1 ).A methodology for correcting these errors has been developed based onestimates of the vertical wind shear and the reflectivity gradient. Lowsignal-to-noise ratios lead to higher random errors (especially in winds) andtherefore the correction (particularly the one related to the wind-shear-induced error) is less effective at low signal-to-noise ratio. Both errorscan be underestimated in our model because the CloudSat data do not fullysample the spatial variability of the reflectivity fields, whereas the ECMWFreanalysis may have smoother velocity fields than in reality (e.g. theyunderestimate vertical wind shear). The simulator allows for quantification of the average number of accuratemeasurements that could be gathered by the Doppler radar for each polarorbit, which is strongly impacted by the selection of the polarizationdiversity H−V pulse separation, Thv . For WIVERN a selection close to20  µ s (with a corresponding folding velocity equal to 40 m s −1 )seems to achieve the right balance between maximizing the number of accuratewind measurements (exceeding 10 % of the time at any particular level inthe mid-troposphere) and minimizing aliasing effects in the presence of highwinds. The study lays the foundation for future studies towards a thoroughassessment of the performance of polar orbiting wide-swath W-band Dopplerradars on a global scale. The next generation of scanning cloud radar systemsand reanalyses with improved resolution will enable a full capture of thespatial variability of the cloud reflectivity and the in-cloud wind fields,thus refining the results of this study.

Doppler W-band polarization diversity space-borne radar simulator for wind studies