Possibilities and limitations using polarimetric observables to detect precipitation regions governed by different growth mechanisms were addressed in this work. Observation by remote sensing provides much better sampling, but the utility of these measurements critically depends on the correct interpretation of the data in terms of the fundamental quantities of interest. In situ probes mounted on an aircraft on the contrary have sufficient resolution to provide detailed information for many purposes, but such observations have limited spatial and temporal coverage.

The Mesoscale Alpine Program (MAP) was partly designed to examine the orographic control of precipitation. During MAP's field phase in fall 1999, measurements were taken during several heavy precipitation events along the southern slope of the Alps. Microphysical data were obtained from a ground-based dual-polarization radar and airborne in situ probes. Remote and in situ data were compared to each other to determine portions of clouds where crystals grew either by riming or aggregation or to detect regions of pristine crystals. Preliminary results look promising to tackle the question whether the riming process in orographically triggered convective cells might increase the precipitation efficiency.