We propose a new approach for groundbased remote sensing of liquid water path (LWP) in the presence of precipitating clouds. Dual polarized groundbased microwave radiometers are capable of detecting the unique scattering signature of nonspherical precipitation sized particles. This polarization signal is only produced by the precipitation particles for which the brightness temperature emission has a different sensitivity to LWP than the smaller cloud drops. By using the information that is contained in the polarization difference of the downwelling brightness temperature the cloud and rain liquid water fractions can be estimated independently. Future retrieval algorithms based on our proposed approach will enable the detection of small precipitation fractions in thick clouds and also allow for estimates of cloud and rain LWP in raining conditions. ¿ 2001 American Geophysical Union