P63     On the diurnal development of Sundowner winds in coastal Santa Barbara, CA.

Duine, Gert-Jan, Earth Research Institute, University of California Santa Barbara, Charles Jones, and Leila MV Carvalho, Dept. of Geography and Earth Research Institute, University of California Santa Barbara

Coastal Santa Barbara occasionally experiences strong and gusty downslope winds that locally are referred to as Sundowner winds. These winds occur on the southern-facing slopes of the Santa Ynez Mountains (SYM), and have intensified all cataloged  major wildfires in the region. Sundowners have a tendency to intensify near sunset, and can occur year-round and under different synoptic conditions . They exhibit dramatic differences in a spatial context: typically, the western side of SYM shows less of a diurnal signal, whereas on the eastern side these diurnal signals are more pronounced. Even though some hypotheses have been made in literature, it is currently unknown what exactly drives this typical timing. This is partly due to the complexity of the terrain upstream of SYM, which consists of relative flat and open upstream terrain on the western part of SYM, a valley that narrows towards the east, and a mountain range (San Rafael Mountains) that varies in distance from the SYM. The possible role of these terrain features upstream of SYM on the diurnal and spatial development of Sundowner winds is investigated by using the WRF model, and, more specifically, by gradually modifying these terrain features upstream of SYM.