Coastal Santa Barbara County (SB) is among the most exposed communities to wildfire hazards in southern California. The Santa Ynez Mountains (SYM) rise abruptly from the coast, separating a cool and stable marine boundary layer on its southern face from a more convective continental boundary layer on its northern face. Downslope windstorms are frequently observed on the southern-facing slopes of the SYM and they have been related to numerous wildfires that disrupted communities on the coast.
These winds, known as Sundowner winds or Sundowners, typically intensify around sunset and remain intense and variable throughout the night. The most intriguing aspect associated with Sundowners is their spatiotemporal variability and consequent challenges in forecasting their behavior. The Sundowner Winds Experiment (SWEX), which extended from 1 April-15 May, 2022, involved 10 institutions and was the first experiment designed to advance understanding and predictability of Sundowner winds, while providing rich boundary layer data sets for developing new theories of downslope windstorms in coastal environments.
Here, I will present the most important scientific questions associated with these winds and will discuss how the integration of sophisticated mobile and in-situ multi-sensor platforms, and model simulations can help to unveil some of the Sundowner’s most unique aspects. Focusing on case studies, we will show differences in mountain winds, and contrast laminar and turbulent flows.
SWEX utilized 18 flux towers, 6 wind lidars, 5 ceilometers, one microwave radiometer, 3-hourly radiosondes from 4 locations, dropsondes and data from a Doppler and Raman lidars on board of the Naval Postgraduate School twin-otter aircraft to characterize and contrast the marine and continental boundary layers. These instruments identified significant variability in the onset and intensity of the winds, and the presence and importance of mountain waves and wave breaking on the spatiotemporal variability of the winds. They revealed the importance of the marine boundary layer in the cycle of the strong winds. More importantly, SWEX data sets represent a unique opportunity to advance understanding of mountain winds and boundary layer dynamics on multiple scales.
Professor Leila M. V. Carvalho was born and raised in Brazil. She obtained her BSc, MSc, and Ph.D. in Atmospheric Sciences (meteorology) from the University of Sao Paulo (USP), Brazil. She was an assistant professor in the Department of Atmospheric Sciences, USP (1998-2008) and began her academic career in the Department of Geography, University of California, Santa Barbara, in 2009.
She leads an interdisciplinary research group “Climate Variations and Change (CLIVAC)” that explores multiple problems related to the Earth’s atmosphere on a wide range of spatiotemporal scales. Her research primarily focuses on extreme weather and climate, mountain meteorology, downslope windstorms, wildfires, and climate variability and change in monsoon systems. https://clivac.eri.ucsb.edu/publications/