Xun (Jerry) Zou

Center for Western Weather and Water Extremes (CW3E), Scripps Institution of Oceanography

Bio: 

Xun (Jerry) Zou graduated from The Ohio State University with a Ph.D. degree in Atmospheric Sciences in 2020 and currently works as an Atmospheric Scientist at the Center for Western Weather and Water Extremes (CW3E), Scripps Institution of Oceanography (SIO). Her research employs high-resolution numerical weather models and observational data to conduct process-based studies of extreme weather events in both Antarctica and the United States. Her ongoing work includes: 1) investigating atmospheric processes contributing to surface melting, with a focus on Atmospheric Rivers (AR); 2) assessing the surface impacts of AR-related extreme weather, including foehn warming, cloud radiative effects, and intense precipitation; and 3) expanding the observation network and enhancing model capabilities for near-surface atmospheric simulations.

Abstract:

Atmospheric Rivers (ARs), narrow corridors that transport concentrated moisture from lower to higher latitudes, significantly impact both mid-latitude and polar regions. In Antarctica, ARs can trigger surface melting that contributes to ice shelf collapse and jeopardize ice sheet stability, while also causing extreme snowfall that offsets ice loss under both atmospheric and oceanic warming. These complex interactions introduce large uncertainties in future projections of Antarctic ice mass balance and global sea level rise. In the western United States, ARs are crucial for water resources and drought relief but have also caused over 80% of flood damage in the past 40 years, with risks expected to escalate in a warming climate. Additionally, recent studies highlight ARs’ influence on water supply and extreme weather in continental interiors. Process-based research is needed to identify the dominant mechanisms that intensify AR-related extremes and to better assess their substantial surface impacts.

In this talk, I will first present a series of combined AR/foehn events over the Antarctic Peninsula during the austral summer from a surface energy balance perspective. Some of these events led to extensive surface melting and ice shelf calving, which could ultimately contribute to glacier failure and Antarctic ice loss. In general, the Antarctic Peninsula can experience four distinct AR patterns, each with varying impacts on the leeside. Sensible heat flux from downslope windstorms and shortwave radiation from foehn clearance dominate leeside warming. However, the abundant moisture, low-level jet, and warmth from the AR intrusion, significantly alter foehn mechanisms. For instance, a fully zonal AR, which would theoretically produce the strongest foehn warming on the leeside, instead enhances moisture transport via gap flow, limiting downward shortwave radiation. This study provides a more accurate estimation of AR impacts on the ice surface over the Antarctic Peninsula. In the second part of the talk, I will cover a bomb cyclone event in March 2019 over Colorado, fueled by a historically strong AR originating from the Gulf of Mexico. This event caused more than 1,400 flight cancellations at Denver Airport and also triggered an ice jam and subsequent flooding on the Niobrara River, which destroyed the Spencer Dam. Experimental model simulations suggested that mid-tropospheric latent heat release coincided with the strength of the warm conveyor belt and played a key role in the deepening of the cyclone. The latent heat release promoted the generation of a lower tropospheric positive potential vorticity anomaly and a stronger low-level cyclonic circulation, enhancing the cyclone, low-level jet stream, and associated water vapor transport. This study identifies key mechanisms which caused rapid intensification of the cyclone and emphasizes AR impacts further inland. It also inspires a new direction for my Antarctic research. I will conclude with my long-term vision for the study of AR-related extreme weather globally, particularly in the context of a changing climate.

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INSTAAR Seminar Series

All seminars are hybrid events, in person in SEEC S228 and via Zoom at 12:00-1:00 pm

Audience: All are welcome

Location: Online and in SEEC S228. 4001 Discovery Drive, Boulder, CO.