Collaborative Research: Extensive Field Observations and Modeling to Understand Multi-band Precipitation Processes within Winter Storms

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Northeast U.S. winter storms have wide ranging societal and economic impacts, especially along the densely populated coastal corridor from Maryland to Massachusetts. Sets of long, thin features with enhanced precipitation rates called snowbands often occur within winter storms and contribute to large variations in snow fall accumulation over short distances. Forecasts for snow accumulation are hampered by gaps in understanding of how snowbands form and are maintained. The project will use high spatial and temporal resolution observations and weather models to resolve the processes within the larger storm that yield snowbands. A set of research instruments located on Long Island, NY will map the 3D storm structures every few minutes. Measurements will address where and when the snow particles grow in the storm. Numerical weather modeling will examine the range of conditions associated with snowband formation and the characteristics of layers in the atmosphere in which the snowbands occur. The findings can help improve forecasting of snowfall accumulation as well as be applied to other geographic regions. The work will focus on intermittent processes for snowband genesis and maintenance. Previous work showed that sets of multiple snowbands can occur with little or no frontogenesis, and the presence of instability did not determine whether bands formed. Additionally, analysis of radar observations did not show clear, sustained convergence signatures to be locked with snow multi-bands implying that multi-bands do not have sustained updrafts throughout their lifecycle. The work will address the role of gravity waves in helping to trigger the release of instabilities at small time and spatial scales that lead in turn to amplifying diabatic feedbacks that form the majority of mesoscale snowbands. The project will collect and analyze high spatial and time resolution observations of snowbands using a set of horizontal and vertical scanning radars, scanning LIDAR, additional sounding launches, high-resolution pressure sensors, and surface snow imagery. The observations will permit examination of the joint interactions over time among released instability, dynamics, and microphysics at spatial scales 1 km and time scales of a few minutes. The project will use modeling to examine the band forcing and stability phase space using a large suite of idealized simulations down to large-eddy scales. This work will provide an improved understanding of banded precipitation within the comma head of extratropical cyclones along the densely populated northeast coast.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.