Enhancement of Santa Ana Winds due to wildfire smoke

The Santa Ana winds are strong warm and dry down-slope airflows blowing from the higher elevation Great Basin to lower elevation southern California coast during late fall and winter. They are driven by the air pressure gradient between the two regions located in the southern edge of a dominant anti-cyclonic system over the western U.S. These winds contribute to severe forest or brush wildfires in southern California, especially under drought conditions. Studies have indicated that smoke particles from wildfires can lead to disturbances in the atmospheric circulation and clouds, and even enhance droughts. Little attentions, however, have been paid to the possible impacts of smoke on Santa Ana winds. This study provides evidence for an assumption that that smoke plume from wildfires could speed up Santa Ana winds near the smoke area. Numerical simulation and experiments were first conducted using a three-dimensional mesoscale meteorological model. The preliminary results indicate the formation in the smoke induced atmospheric disturbances of a cyclonic circulation over the offshore region with easterly winds in southern California. An atmospheric dynamical model with aerosol radiative forcing was then used to analyze atmospheric disturbances. The analytical solutions of the model indicate warm temperature, ascending vertical motion, and cyclonic circulation in the atmospheric perturbations with strong absorptive smoke aerosols. Observational evidence was also sought.