ProF. Leila Carvalho of UCSB Geography

Abstract: Coastal Santa Barbara is considered one of the most idyllic locations on the North American West Coast, but its beauty is frequently disrupted by fast-spreading, wind-driven wildfires. The east-west oriented Santa Ynez Mountains (SYM), rising abruptly over 1,000 meters from the coastal plain, create a distinct climatic environment by separating the cool, stable air over the Pacific from the much drier atmosphere of the Santa Ynez Valley. This topography leads to unique regional wind patterns, including the Sundowner winds, which occur along the southern slopes of the SYM. Named for their typical onset from late afternoon to early evening, Sundowners can reach wind speeds exceeding 50 mph. These winds rapidly dry the air and elevate nighttime temperatures, dramatically exacerbating wildfire risk. Sundowners have played a critical role in intensifying all major wildfires in coastal Santa Barbara and represent the region's most significant fire-weather phenomenon. Their spatial and temporal variability, driven by complex interactions between synoptic systems, topography, and the marine boundary layer, presents major forecasting challenges. Accurate predictions are vital for issuing red-flag warnings, assessing wildfire risks, and planning evacuation and firefighting strategies. Our research advances wildfire resilience by integrating regional models with diverse observational datasets to advance understanding and improve forecast of Sundowner winds. We collaborate with the National Weather Service LA/Oxnard office, which issues red-flag warnings and coordinates actions with local fire agencies. While Sundowners are unique to Santa Barbara, our studies have identified mechanisms common to other coastal downslope windstorms, offering broader insights into fire-weather dynamics and risk mitigation in vulnerable regions.

Biography:

Bio: Dr. Leila Carvalho is a Professor in the Department of Geography and a Researcher at the Earth Research[RF1]  Institute, UCSB. She holds B.S., M.Sc., and Ph.D. degrees in Atmospheric Sciences from the University of São Paulo, Brazil. Her research focuses on regional and large-scale climate variability and change, including monsoon dynamics, tropical-extratropical interactions, extreme precipitation and temperature events, mountain weather and climate, and regional modeling. Additionally, she studies downslope windstorms in Southern California, such as Sundowners and Santa Ana winds, and their impacts on wildfires. She is also interested in extreme precipitation in complex terrain and atmospheric rivers.

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