Comparison of Disdrometer and X-band Mobile Radar Observations in Convective Precipitation

Microphysical data from convective thunderstorms are sparse, yet they are essential to validate microphysical schemes in numerical models. Mobile, dual-polarization X-band radars are capable of providing data on radar reflectivity factor, droplet shape, and hydrometeor type, which can be used for validation purposes. However, X-band radars suffer from radar beam attenuation in heavy rainfall and hail, which can be partially corrected with attenuation correction schemes. In this research, we use surface disdrometer observations to validate the performance of a differential phase-based attenuation correction scheme that is applied to data recorded by the National Oceanic and Atmospheric Administration's (NOAA), X-band, dual-Polarized (NO-XP) mobile radar, which was deployed during the second Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX2). A hydrometeor classification scheme for X-band radars is also compared to a new hydrometeor classification scheme for disdrometers. Results are presented from five supercell thunderstorms and one squall line (183 minutes of data). After the radar data are corrected for attenuation, 37% (42%) of the reflectivity (differential reflectivity) observations, respectively, are within the sampling uncertainty of the disdrometer measurements. A comparison of the hydrometeor type observed by the two instruments is also presented, in which the same liquid precipitation (ice) class is assigned 75% (66%) of the time. Good agreement between the instruments corresponds to observations that have a large radar signal-to-noise ratio and that were recorded in horizontally uniform precipitation without large hail.