Observational and Numerical Modeling Study of Downburst Generation Using Dual-Polarization Radar

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This project is to study a hazard weather phenomenon known as downbursts. The Downbursts are rapidly descending columns of air that can cause strong, damaging winds that pose a threat to aviation, infrastructure, livestock, and human life. Meteorologists rely on weather radar data to detect developing downbursts, but because they are relatively localized and can develop quickly, it is often difficult to issue warnings for them in advance. However, recent advancements in radar technology now permit improved insight into the factors that lead to downbursts, but a comprehensive study examining such signatures has yet to be performed. By better understanding the causes of downbursts and what these factors look like in their existing radar data, forecasters will be able to better anticipate their occurrence and intensity before they reach the ground, and thus provide earlier warnings with fewer false alarms and more time for people to safely seek shelter. In addition, as computers play an increasingly large role in deciding when to issue severe weather warnings, the insights gained from this study will help determine how reliably weather models simulate downbursts and provide the basis for future automated downburst detection. The project involves mentoring a graduate student to be the next generation of atmospheric scientists. This study seeks to use both observations and numerical simulations of downbursts in a complementary manner to understand the relation between the sources of negative buoyancy that drive downbursts and their manifestation in observed dual-polarization radar variables. A novel cell-tracking algorithm will be used to comprehensively survey the polarimetric characteristics of downbursts and their variability across a variety of thermodynamic environments and geographic regions. Additionally, a one-dimensional model with spectral bin microphysics that is coupled to a forward polarimetric radar operator will then be used to simulate downbursts and quantitatively examine the association between the environment, sources of negative buoyancy (i.e., precipitation loading and diabatic cooling), and the resultant downburst intensity with the evolution and spatial distribution of the simulated polarimetric variables. Informed by the findings of the first two components, the third part of this study will evaluate the ability for existing convection-resolving models with bulk microphysics schemes to realistically simulate downbursts and identify any deficiencies limiting their usefulness.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.