Downslope Windstorms in Coastal Environments and Interactions with the Continental and Marine Boundary Layers: Lessons Learn from the Sundowner Winds Experiment (SWEX-2022), Santa Barbara, CA

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 coastal SB separating the Pacific Ocean on its south face from the Santa Ynez Valley on its north face. Downslope windstorms are frequently observed on the southern-facing slopes of the SYM. These winds typically intensify around sunset and throughout the night, and are known as Sundowner winds or Sundowners. The Sundowner Winds Experiment (SWEX) was a field campaign involving 9 institutions and 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. Sundowner spatiotemporal characteristics are controlled by complex interactions among atmospheric boundary layer processes occurring upstream, in the Santa Ynez Valley, and downstream associated with a cool and stable marine boundary layer. The SWEX campaign (April 1st- May 15 2022) was designed to enhance spatial measurements to resolve local circulations and vertical profiles from the boundary layer to the mid-troposphere, and from the SB channel to the Santa Ynez Valley. These observations allowed testing hypotheses concerning the mechanisms controlling Sundowner winds, evaluate mesoscale simulations and improve lead time forecasts of Sundowners. In this talk, we will discuss the integration of observations provided by sophisticated mobile and in-situ multi-sensor platforms and flux towers with focus on case studies during the experiment. Using multiple lidars, we will show differences in mountain winds, contrasting laminar (next to mountain slopes) and turbulent (wave breaking region) flows. We will use 20 flux towers, 6 ceilometers and 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. We will also use these data sets to demonstrate the presence and importance of mountain waves and wave breaking on the spatiotemporal variability of the winds. This talk will focus on contrasting conditions associated with strong winds in the eastern and western portions of the SYM.