CEE Seminar (ZOOM): Critical Fire Weather and Wildfires in Santa Barbara, California - Lessons Learned from Models and Observations

Abstract: Wildfires in California have increased in size, intensity and frequency in recent years due to natural and anthropogenic reasons, including (but not limited to) climate change, forest management and a growing community living in the wildland-urban interface. Coastal Santa Barbara County (SB), with a population exceeding 130,000 inhabitants, is among the most exposed communities to wildfire hazards in Southern California. Several unique aspects contribute to this reputation. The Santa Ynez Mountains (SYM), the main topographic feature of the region, rise abruptly from coastal SB with a unique east-to-west orientation and with elevations exceeding approximately 1000 meters. These mountains separate the cool and stable air from the Pacific Ocean on its south face from a drier, and often hotter and less stable air in the Santa Ynez Valley (SYV) on its north face. Moreover, the San Rafael Mountains (SRM), with elevations exceeding 2000 meters, merge with the SYM on its eastern side, giving the SYV a V-shape. This unique landscape creates conditions for the development of local circulations with contrasting characteristics over short distances. Downslope windstorms frequently observed on the southern slopes of the SYM are known as ”Sundowner winds” (or Sundowners) due to their typical onset around sunset. Nonetheless, many other peculiarities characterize these winds. Sundowners exhibit remarkable spatiotemporal variability along the approximately 100 kilometers long slopes of the SYM and this variability is critical during wildfires. This presentation will show some of the most recent results based on 30 years simulations with the Weather Research and Forecast (WRF) model. I will show evidence of the existence of three distinctive Sundowner regimes and discuss our main hypothesis for the timing of Sundowners. I will also show results from a pilot experiment that provide important insights on the vertical structure of the winds. Finally, I will show the importance of observations in the region to enhance our ability to observe, characterize and predict critical fire weather regimes and how this can contribute to increase resilience to wildfires in the region. 

Bio: Leila Carvalho is a professor of meteorology and climate at UC Santa Barbara. She obtained her M.Sc. and Ph.D. in atmospheric sciences from the University of Sao Paulo, Brazil. She was assistant professor at the University of Sao Paulo from 1998-2008 and joined the Department of Geography at UCSB in 2009. Her research interests focus on mountain meteorology and wildfires, climate variability and change in monsoon regions, and extreme events on multiple scales. She leads the “Climate Variability and Change” (CLIVAC) group at UCSB. She is co-chair of the CLIVAR/GEWEX global monsoon panel.