Comparison of Aircraft Measured Microphysics with Down-looking Multifrequency Radar During IMPACTS

The Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) is a 5-year study of winter snowstorms in the northeast U.S. with three field campaigns in per year in January-February 2020-2023. Two aircraft were flown during IMPACTS 2020, the NASA P-3 instrumented with microphysics probes, and the NASA ER-2 with three nadir-looking Doppler radars covering X, Ku, Ka, and W-band. The two planes flew closely coordinated flight tracks as often as possible, allowing for fairly coincident ER-2 radar reflectivity and Doppler measurements. The P-3 in-situ measurements, that included particle probes and bulk water measurements-the WISPER probe, which measured the condensed water content (CWC), and the TAMMS instrument that measures air vertical air velocity. The focus of this presentation is to investigate to how accurately we can estimate quantities such as ice content, vertical air velocity, and particle fallspeed from the radar measurements for the collocation periods. With sufficient accuracy, we can derive these properties in regions where there are no in-situ measurements. This is otherwise difficult due to the variety and complexity of ice habits, bulk densities, etc. in regions with radar data alone. In this work, the IMPACTS particle size distributions are used to estimate reflectivity, ice content, and mean Doppler velocity using radiative transfer calculations for the ER-2 radar wavelength. These estimated quantities are then compared with measured reflectivity at 4 frequencies, and the measured CWC. To accomplish this, we have constructed a data base that includes all coincident ER-2 radar and P-3 measurements during IMPACTS. These measurements will be used to validate the reflectivity estimated from the microphysics measurements, and reflectivity-weighted fallspeed estimates needed for the Doppler measurements. The ER-2 measured Doppler velocity consists of vertical air motion + reflectivity-weighted fallspeed, so the P-3 air motion will be used to back out fallspeed. We will discuss the results of these comparisons from the first of three IMPACTS field campaigns.