Diagnose and Understand the Mechanisms behind Warm Season Extreme Weather over Central and Intermountain United States

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Extreme weather, such as persistent dry spells, heatwaves, fire weather, is a major cause of natural disasters. Its impacts on lives, public health, economy, and environment have been escalating rapidly in recent decades. For example, the wildfires in 2018 over California, induced by intensive fire weather, have caused over $126.1-192.9 billion economic loss. Yet, we do not fully understand its underlying causes. For example, the following questions are still perplexing the scientific community. Why do extreme events occur sometimes, but not at other times under similar atmospheric flow patterns? Why do warm season extreme dry spells and hot days occur together sometimes, but not at other times? Why do some extreme weather types, such as fire weather during the largest wildfires in western United State, appear to become less explainable by the synoptic circulation since 2000 compared to those from the time in the 1980s’ and 90s’? This project will apply state-of-the-art statistical analyses to capture the variety and complexity of the synoptic wind patterns responsible for the extreme events. More importantly, the roles of clouds, precipitation, and aerosols relative to atmospheric dynamic process in intensifying extreme weather will be investigated. Furthermore, an integrated approach will be applied to systematically characterize the atmospheric physical and dynamic processes and land surface feedbacks behind extreme dry and wet spells, hot days, fire weather and floods. The multifaceted and integrated approach will clarify the relative roles of the atmospheric dynamics and physical processes in determining extreme weather and concurrence of multiple extreme weather types. Such an approach could lead to a paradigm shift from event-based and synoptic-circulation-focused approaches that have dominated the literature in this research area, and significantly advance our understanding of extreme weather, especially for that which cannot be sufficiently explained by synoptic circulation anomalies. The project will train a woman PhD student, undergraduate summer research interns, and a postdoctoral researcher, and incorporate its research results into a large upper-division undergraduate science course. These activities will contribute to the NSF educational mission and future workforce of physical and dynamic meteorology. The proposed public outreach through media will enable the PI to translate the latest research result about extreme weather from this project to meaningful or even actionable information for society. The project was co-funded by NSF Physical and Dynamic Meteorology and Climate and Large-scale Dynamics programs. 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.