Airborne Radar and Microphysics Signatures in Snowbands as Measured during the IMPACTS Field Campaign

Snowfall in winter storms is unevenly distributed, often organized in banded structures of higher intensity snowfall manifested as regions of local maxima in radar reflectivity. These so-called snowbands vary in intensity, size, and structure from storm to storm and within individual storms. The processes that contribute to their organization, evolution and life cycle are not well understood. To fill this knowledge gap, the NASA Earth Venture Suborbital-3 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign collected measurements in storms that occurred in the Northeast and upper Midwest regions of the United States and Canada across three winter seasons, from 2020 through 2023. Thirty-five individual storms were sampled by aircraft and ground assets. The aircraft included a satellite-simulating high-altitude ER-2, which was equipped with radars sampling cloud and precipitation characteristics at four frequencies (X-, Ku-, Ka-, and W-band), 2 radiometers measuring radiances across microwave and sub-millimeter wavelengths, a cloud physics lidar, and a lightning detection system. The in-situ P-3 aircraft flew in coordination with the ER-2 and sampled cloud, precipitation and environmental parameters within the cloud at varying altitudes. The P-3 was equipped with multiple cloud microphysics probes, instruments measuring flight-level meteorological parameters such as temperature, humidity and winds, and a dropsonde system. The aircraft measurements were supplemented with mobile and fixed radar systems and sounding teams, and the New York mesonet surface data. Operational data such as National Weather Service surface observations, soundings at fixed sites, and GOES-16 satellite data rounded out the observational network. Together these data provide an assessment of the cloud precipitation, and snowband structures and evolution for a wide variety of storm systems across the Midwest and Northeast. This presentation will highlight preliminary results from events across all three deployment seasons, with emphasis on the data obtained from the multi-frequency airborne radars on the ER-2 along with coordinated P-3 in situ microphysics data. Documenting the microphysical properties in regions of prominent dual-frequency ratio (DFR) derived from the ER-2 radars in winter storms provides valuable information on the interpretation of the remote measurements. Prior work explored regions of prominently higher Ku- and Ka-band DFR at the P-3 aircraft location using data from the first deployment season 2020. Regions of prominently higher DFR were found to have 60% larger mass-weighted mean diameter, 33% smaller effective density, and 79% lower normalized intercept parameter than in regions with low DFR. These findings are being tested with data from the 2022 and 2023 deployments. The relationship between regions of higher DFR and snowbands as traditionally defined by Plan Position Indicator (PPI) scans from polarmetric operational ground-based radars are also being examined with IMPACTS events. Processes that can contribute to snowbands, such as frontogenesis and conditional instability, are also being investigated with airborne measurements, including flight-level vertical motions from the Turbulence Air Motion Measurements (TAMMS) on the P-3 and Doppler velocities derived from nadir pointing radars on the ER-2.