Multi-frequency radars offer enhanced detection of clouds and precipitationcompared to single-frequency systems, and are able to make more accurateretrievals when several frequencies are available simultaneously. Anevaluation of a spaceborne three-frequency Ku-/Ka-/W-band radar system ispresented in this study, based on modeling radar reflectivities from theresults of a global cloud-resolving model with a 875 m grid spacing.To produce the reflectivities, a scattering model has been developed for eachof the hydrometeor types produced by the model, as well as for melting snow.The effects of attenuation and multiple scattering on the radar signal aremodeled using a radiative transfer model, while nonuniform beam filling isreproduced with spatial averaging. The combined effects of these are thenquantified both globally and in six localized case studies. Two differentorbital scenarios using the same radar are compared. Overall, based on theresults, it is expected that the proposed radar would detect a high-qualitysignal in most clouds and precipitation. The main exceptions are the thinnestclouds that are below the detection threshold of the W-band channel, and atthe opposite end of the scale, heavy convective rainfall where a combinationof attenuation, multiple scattering and nonuniform beam filling commonlycause significant deterioration of the signal; thus, while the latter can begenerally detected, the quality of the retrievals is likely to be degraded.
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