An Analysis of the Microphysical and Thermodynamic Properties of Generating Cells Within Snowbands Associated With Winter Storms Observed During IMPACTS

In-situ and remote sensing observations of snowbands were obtained by probes on a cloud-penetrating NASA P-3 and a high-altitude NASA ER-2 aircraft, respectively, to identify and characterize generating cell (GCs). This was during the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign in 2020. The radar reflectivity and Doppler velocity measured by a Cloud Radar System (CRS) on the ER-2 were used to identify GCs for time periods when the horizontal separation between the ER-2 and the P-3 was less than 1.4 km, with the characteristics of small-scale air motion subsequently determined by the Turbulent Air Motion Measurement System (TAMMS) on the P-3. Through a case study analysis of collocated regions with radar confirmed GCs, an algorithm that considered the statistical significance of the range in small scale vertical velocity measurements from the TAMMS, as well as the magnitude of the largest velocity values, was developed to identify GCs using data exclusively recorded by the TAMMS. Using time periods identified as GCs from the TAMMS for the entire 2020 IMPACTS campaign, cloud microphysical properties derived from the Rosemount Icing Detector (RICE), Fast Cloud Droplet Probe (CDP), 2D-S Stereo Probe (2DS), and the High-Volume Precipitation Spectrometer (HVPS) installed on the P-3 were used to characterize the cloud microphysical properties inside and between GCs. Cloud penetrations were defined as a sequence of 18 second time intervals where the P-3 encountered cloud particles at least once every 6 seconds, until this criteria was no longer met. Of the 94 instances of cloud penetration by the P-3 considered during analysis, 29 contained at least one GC. Contrary to previous observations in winter storms, distributions of IWC and mass-weighted mean particle dimension were not statistically different for data collected within and between GCs, even when considering the large number of datapoints, but mean number-weighted particle dimensions were 0.35_mm larger between GCs than within. Temperatures were on average 2.4°C greater, and dewpoint depressions were 0.77°C smaller within GCs than between. There was a 9% decrease in supercooled liquid water (SLW) presence between GCs compared to within. SLW was detected within all TAMMS confirmed GCs. The means for defining GC regions in a substantiated way with in-situ measurements depends on the reliability of contrasting data recorded from the ER-2 and P-3 aircraft during collocated time periods, as well as the number of collocated time periods available. It is because of these limitations, and the unconventional means for detecting GCs using the TAMMS, that differences in the observed characteristics of TAMMS-confirmed GCs may be present, when compared to previous studies. In this presentation, we will discuss this novel approach to GC identification, as well as the observations within those GCs and how they differ from results using alternate approaches.