Wind-driven Rainfall Microphysics: Raindrop Shape - Fall Velocity - Size Distribution under Wind Shear and Turbulence

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Knowledge of the characteristics of raindrop size and shape is important for weather radar estimates of rainfall. Rainfall droplets can change in shape and speed as they fall to the ground, especially in situations where there are collisions with other droplets. This project will enable researchers to collect very high-resolution observations of raindrops and determine how they are affected by wind. Improved estimates of rainfall from weather radars will potentially impact flood forecasting and water resource management. The project also involves training and mentoring of early-career scientists, ensuring a diverse and highly capable future workforce.The research team will conduct an observational and analysis-based study to uncover the effect of wind on rainfall microstructure and whether microphysical quantities under the influence of wind can be predicted. Data for the study will come from a field site near UT-San Antonio, which includes the High-speed Optical Disdrometer (HOD) and other meteorological instruments. The project will address four main hypotheses: 1) Wind shear and turbulence induce flow/pressure field alterations/fluctuations around raindrops, 2) These alterations/fluctuations cause raindrop fall velocity deviations from predicted terminal values, 3) Broadening of the raindrop fall velocity distributions increases the raindrop-raindrop collision rates, and 4) Increased collision rates intensify drop size distribution evolution.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.