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Microphysics and Dynamics of Snow Band and Generating Cells from IMPACTS: Snow Production Rates
This study uses in-situ and coincident overflying aircraft data from the NASA IMPACTS field program to study the role of snow band and generating cell dynamics on the production of snow from East Coast United States snowstorms. Data from field programs in 2020, 2022 and 2023 are used in this analysis. In-situ data, including microphysical probe measurements over a wide range of particle sizes, and 3D wind measurements and water vapor measurements, are collected from the NASA P3 aircraft. Snowfall rates are calculated from the particle probe size spectra measurements, drawing on the particle images and direct measurements of the condensed water content to estimate particle mass. Remote sensing data-Doppler radar measurements for X, Ku, Ka and W bands are used to refine the estimates of snowfall rates and their vertical distribution through the cloud depth.
Vertical motions are found to be in the range -2 < w < 4 m/s. Snowfall rates are enhanced in the updraft regions, with increasing rates with vertical velocity. The liquid water content scales with the vertical velocity. The particle size distributions within the snowbands are broader than those outside of the snowbands. The Doppler radar measurements-reflectivity, provides a means of determining the increase in snowfall rates as a function of temperature and vertical velocity. Data from many snow bands sampled over the three years are synthesized to provide an illustration of the growth of snow in snowbands.
