|Title||Climate change suppresses Santa Ana winds of Southern California and sharpens their seasonality|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Guzman-Morales J., Gershunov A|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||10 km card10; Geology; reanalysis; Santa Ana Winds; Santa Ana winds future projections; seasonality change; temperature; united-states; variability|
We downscale Santa Ana winds (SAWs) from eight global climate models (GCMs) and validate key aspects of their climatology over the historical period. We then assess SAW evolution and behavior through the 21st century, paying special attention to changes in their extreme occurrences. All GCMs project decreases in SAW activity, starting in the early 21st century, which are commensurate with decreases in the southwestward pressure gradient force that drives these winds. The trend is most pronounced in the early and late SAW season: fall and spring. It is mainly determined by changes in the frequency of SAW events, less so by changes in their intensity. The peak of the SAW season (November-December-January) is least affected by anthropogenic climate change in GCM projections. Plain Language Summary Dry and gusty Santa Ana winds (SAWs) drive the most catastrophic wildfires in Southern California. Their sensitivity to the changing climate has been a matter of uncertainty and debate. We have assessed the response of SAW activity to global warming and describe these results in detail here. The overall decrease in SAW activity robustly projected by downscaled global climate models is strongest in the early and late seasons-fall and spring. SAWs are expected to decrease least at the peak of their season approximately December. Importantly, decreased SAW activity in the future climate is driven mainly by decreased frequency rather than the peak intensity of these winds. These results, together with what we know from recent literature about how precipitation is projected to change in this region, suggest a later wildfire season in the future.
In light of these projections, the largest wildfire in SoCal history (Thomas Fire) occurring in December 2017 and fanned by back‐to‐back Santa Ana winds (SAWs) events is likely a harbinger of wildfire seasonality we would expect to experience more often in the future. In December, back‐to‐back SAWs are most probable providing opportunities for wildfires to burn longer and bigger. In the future, the probability of back‐to‐back events will diminish somewhat, but will still remain much stronger in December than it ever was in October or even November.