Comparison of Lake-Effect Snow Precipitation Rates Determined from Radar and Aircraft Measurements

Snow-particle size-mass relations derived from radar reflectivity and particle-size spectra obtained from Particle Measuring Systems (PMS) probes in nonconvective clouds predict greater masses for large particles than are indicated by most direct measurements of particle size versus mass. This may be a result of the reduced sensitivity of PMS probes to thin or narrow parts of snow particles and to the inclusion of large numbers of irregular and partially rimed particles. Comparisons were made of snow precipitation rates calculated from the effective reflectivity factor measured by a ground-based radar and those estimated from simultaneously measured PMS 200Y probe snow-particle-size spectra for 134 samples from 3 days in lake-effect snow over Lake Michigan. Results show the best agreement when PMS 200Y spectra are used with a size–mass relation similar to those derived from combining reflectivity and PMS probe-measured spectra. Commonly used size–mass relations obtained from direct measurements of particle diameters and masses, when used with PMS 200Y spectra, consistently underestimated snow precipitation rates in these samples.