Year: 2025
Type: article
Abstract: Numerical model predictions of precipitation rates rely heavily on representations of how fast hydrometeors fall, assuming settling is determined only by the opposing force balance of gravity and drag. Here, we use a novel suite of ground‐based winter measurements to show large departures of the mean snowflake settling speed from the terminal fall speed of a particle falling broadside. Where is lower than the air root‐mean‐square turbulent velocity fluctuation , settling is sub‐terminal by up to a factor of five, and if it is higher, then settling is super‐terminal by up to a factor of three. Mean winds and aerodynamic lift appear to play an unexpectedly important role, by tilting snowflake orientations edge‐on while slowing their mean rate of descent. New parameterizations are provided for relating winds and small‐scale turbulence to hydrometeor orientations, drift angles, and precipitation rate reductions and enhancements.
Source: Geophysical Research Letters
DOI: 10.1029/2025gl114780
Institution: University of Utah
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,190
Funder: National Science Foundation
OpenAlex ID: W4411373934