CAREER: Advancing the Understanding of Turbulence-Microphysics Interactions in Clouds Through Multiscale Numerical Modeling

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Clouds are critical for many processes in the Earth system, including precipitation formation, water resources, and climate feedbacks; the role of clouds is a major source of uncertainty in present and future climate. Computer models of weather and climate often fail to accurately capture the effects of random, turbulent fluctuations of temperature, humidity, and wind speed on cloud droplet formation and growth. These turbulent fluctuations can impact cloud lifetimes, precipitation formation, and climate feedbacks and therefore are important to model accurately for both weather and climate prediction. The central aims of this project are to understand the small-scale interactions between turbulence and cloud droplet formation and growth and to improve the representation of these processes in weather and climate forecasting models. The educational component of this project is intended to increase engagement of undergraduates from physics and other STEM fields in atmospheric science through the development of lesson plans following principles of authentic instruction. These lessons will be piloted by instructors at teaching-intensive Oklahoma universities and are intended to promote interest in the geosciences among a diverse pool of undergraduate students. Despite the importance of small-scale interactions between turbulence and microphysical processes in clouds, these interactions remain poorly represented in both large eddy simulations and weather and climate forecasting models. Using direct numerical simulations (DNS) that capture the formation and growth of millions of Lagrangian droplets in a turbulent flow, the researchers will develop new subgrid-scale models for turbulence-microphysics interactions that accurately capture the governing physics. These subgrid-scale models will be validated against DNS and laboratory cloud chamber data; the resulting large eddy simulations will be used to investigate the extent to which interactions between turbulence and microphysics—at spatial scales larger than those attainable in DNS—influence cloud lifetimes, precipitation formation, albedo, and other large-scale cloud properties.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.