A104-09
Changes in Fire Potential and Extreme Downslope Winds in California under Global Warming Projections of 1.5 °C, 2.0 °C, and 3°C

Thursday, 10 December 2020: 18:02
Virtual
Yi-Chin Liu, California Environmental Protection Agency Air Resources Board, Sacramento, CA, United States, Pingkuan Di, Air Resources Board, Sacramento, CA, United States, Shu-Hua Chen, University of California Davis, Davis, CA, United States, Xue Meng Chen, California Air Resources Board, Sacramento, CA, United States and Jeremy Avise, Washington State University, Civil and Environmental Engineering, Pullman, WA, United States
Recorded Presentation
Abstract:
The Paris Agreement aims to constrain global mean temperature (GMT) to a maximum of 2°C above pre-industrial levels, with an aspirational target of 1.5°C. Even though the proposed targets have inspired numerous studies to assess corresponding climate changes for different regions across the world, the impact on fire weather in California is not well understood. This study explores the potential changes in fire potential and extreme downslope wind occurrences, including Diablo Winds (DW) in Northern California and Santa Ana Winds (SAW) in Southern California under 3 different climate scenarios, namely a GMT increase of 1.5°C, 2°C, and 3°C respectively.

In this study, we use data from the Climate of the 20th Century Plus Detection and Attribution project. The data are produced using the Community Atmospheric Model version 5.1 configured at a global resolution of approximately 0.25°. There are five ensemble members available for base-year runs (1996-2015) and projected runs (2106-2115) with a GMT increase of 3°C, and 6 members each for projected runs with a GMT increase of 1.5°C and 2.0°C, respectively. To validate the performance of the base-year runs, we calculate the DW and SAW occurrences using the mean of ensemble members and compare results to a similar analysis using three reanalysis datasets. The results show that the base-year runs reasonably capture the spatial distribution of DW-like events, high occurrence of SAW-like days along the coastal region, and monthly variations of DW and SAW occurrences. This validation provides us the confidence to use the associated data (future projections) for our study.

Our results project an increase of high fire potential days from the months of September to December, and a decrease from January to March for all three GMT scenarios compared to the base-year runs. In addition, the three GMT scenarios consistently show that (1) November has the largest increase in frequency of high potential fire days, and (2) California’s North Coast has a higher frequency increase compared to the South Coast. We also find that the +1.5 and +2.0 GMT scenarios project an increased frequency of DW and SAW, but the +3.0 GMT scenario unexpectedly projects a decreased frequency of DW and SAW. The inconsistencies of trend of extreme downslope wind occurrences between +2.0 and +3.0 GMT are probably caused by different responses of pressure systems and jet streams to the changes in temperature.

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