The response of passive microwave observations toice particle scattering and surface emissivity has been studied for frequenciesat 85, 150, and 183 GHz. Using two- and three-dimensional simulations of differentprecipitation events, we found that a channel around 150 GHz generally exhibitsthe strongest scattering signature due to precipitation-sized ice particles.This channel is only moderately affected by variations in surface emissivity.The sensitivity of the 150 GHz channel to variations in cloud water is about25 (Kg-1 m3). In comparison, the sensitivityto changes in surface emissivity is about 5 K/(10%) for cold, dry atmospheresand less than 1 K/(10%) for typical midlatitude atmospheres. Channels at around85 GHz are much stronger affected by variable surface emissivity (sensitivitiesare up to 15 K/(10%) and show on average a 2 to 2.5 times smaller scatteringsignature (10 Kg-1 m3). The sensitivityof a water vapor sounding channel at 183--7 GHz to ice particle scatteringstrongly depends on the environmental conditions but is in general about afactor of 1.5 to 2.5 smaller than at 150 GHz. This is due to the contributionof water vapor in and above the cloud to total emission, masking the scatteringsignal. The weighting functions of channels at 183--3 and 183--1GHz peak too high up in the atmosphere and only show a weak or negligibleresponse to the precipitation events under investigation. Based on these results,frequencies around 150 GHz, possibly in combination with channels at 85 and183--7 GHz seem most appropriate for the detection and retrieval of precipitationproperties at middle and high latitudes.