Wildland fires in Southern California: climatic controls and future prediction

Transcription

1 Wildland fires in Southern California: climatic controls and future prediction Yufang Jin Department of Earth System Science University of California, Irvine SCSRA 6 th Annual Workshop May 3, 13

2 Large Fires in Southern California Santa Ana Fires Summer Fires Santiago Canyon Fire, October, 7 Station Fire, August 9, 9

3 Diverse ecosystems and large wildland urban interface

4 Wind patterns from km WRF 1 6 # SA days #SA events Averaged over all days with SAi=8 J F M A M J J A S O N D

5 Fire prone landscape up to 1

6 Interannual variation Summer: JJA Burned Area Fall: SON Events: from NOAA extreme events report

7 Motivation Large and destructive fires over the past decade Fire prone diverse landscape: shrub, sever fire weather, rugged terrain Large wildland urban interface (WUI) Understand seasonal and interannual variation in contemporary fires (fire climate vegetation human interactions) Predict future change and impacts Implications for planning and management

8 Santa Ana event and fire weather with High resolution climate data Sat>6m/s Composite Wind Speed Map (1981 )

9 Seasonality: fire and climate Number of fires (#/yr) BA (1 3 Acres/yr) SA non SA All Mean fire size (1 3 Acres) J F M A M J J A S O N D 15 J F M A M J J A S O N D T (C) #SA events RH(%) 3 4 # SA days Wind Speed (m/s) J F M A M J J A S O N D

10 Fire frequency Fire freq. Summer fires (May, Jun, Jul, Aug, Sep) Fosberg Fire Weather Index Santa Ana fires (Sep, Oct, Nov, Dec)

11 Long Term Trends in S. California Fires Summer fires Santa Ana fires

12 Climatic controls: summer fires r =.6 Obs. Predicted Fire Size (1 3 Acres) c) r =.4 Normalized influence 3 d) 1 RH Winter PPT Tmax Fire Spread Year Year

13 Climatic controls: Santa Ana fires Obs. Predicted Fire Size (1 3 Acres) c) Normalized influence d) RH Fire Spread Year Year

14 Climatic controls: burned area Summer Burned Area (1 3 acre) Santa Ana Burned Area (1 3 acre) e) Year e) r =.5 r =.8 Obs. Predicted Year Normalized influence Normalized influence 3 f) Year 1 f) Year

15 Key points for climatic controls Number of fires: cumulative precipitation and Tmax for summer fires; RH and current precipitation for Santa Ana fires. Fire size: RH, winter plus current precipitation, and Tmax for summer fires; RH for SA fires (e.g. for 3 and 7 extremes); and wind speed was significant for both July and October fire size. Extreme fire years correlated mostly with stronger SA events (lower RH and stronger wind, e.g. 3, 7 Oct, and 197 Sep) Aggregated to seasonal scale, burned areas were mainly controlled by RH and Tmax for summer fires, and by RH for Santa Ana fires. Statistical model based only on climate can capture up to 6% of variation in # fires and burned area (r =.8). Changes in relative humidity (especially in fall) and Tmax (in summer) in the future will affect the Southern California s fires.

16 Region Current-day run Climate change run (RCP8.5 Business as usual ) Southern California (NARR Reanalysis) 41-6 (NCAR CESM)

17 Warming by Mid Century Considerable in S. California Mountains 45 6 minus RCP8.5 scenario from CESM downscaled using WRF S. Capps, A. Hall, and Y. Jin

18 Drying by Mid Century 45 6 minus RCP8.5 scenario from CESM downscaled using WRF

19 Current (1986 ) and Future (45 6) Climate 4 1 T (C) PPT (mm per mon) J F M A M J J A S O N D J F M A M J J A S O N D RH (%) 45 4 Wind speed (mph) J F M A M J J A S O N D 6.5 J F M A M J J A S O N D

20 Current (1986 ) and Future (45 6) Number of fires per year Present Future Summer Fire Estimates 3 Controls relative to contemporary Temperature Precipitation Cumulative precip RH Total Fire size (1 3 acres/year) May Jun Jul Aug Sep Controls relative to contemporary May Jun Jul Aug Sep Temperature Precipitation Wind speed RH Total May Jun Jul Aug Sep May Jun Jul Aug Sep

21 Current (1986 ) and Future (45 6) Santa Ana Event Climate 1 8 Present Future # SA days 6 4 J F M A M J J A S O N D RH (%) Wind speed (mph) J F M A M J J A S O N D 1 J F M A M J J A S O N D

22 Current (1986 ) and Future (45 6) Santa Ana Fire Estimates Present Future Number of fires per year 1 5 Sep Oct Nov Dec Burned area (1 3 acres/yr) Fire size (1 3 acres/year) 3 5 Sep Oct Nov Dec 1 Sep Oct Nov Dec * Holding precipitation unchanged

23 Current (1986 ) and Future (45 6) Burned Areas: Summer and Santa Ana Fires Present Future Burned area (1 3 acres/yr) Burned area (1 3 acres/yr) May Jun Jul Aug Sep Sep Oct Nov Dec

24 Conclusions and Future goals Importance of climate control in fires: summer and SA fires Extreme fire weather critical for Santa Ana fires Summer fires are likely going to increase by mid Century Late season SA fires may increase slightly How does changes in fire regime and climate affect vegetation? What are the subsequent impacts of Santa Ana fires (vs. summer fires) on air quality and human health? Which communities are most vulnerable to climate change and fire impacts? How do human activities affect fires?

25 Acknowledgement Funding source NASA Interdisciplinary Sciences Collaborators Jim Randerson, Mike Goulden (UCI) Alex Hall, Qinbin Li, Scott Capps (UCLA) Simon Hook (JPL)

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27 Simulated Burned Areas Burned Area (1 3 acre) 3 1 Summer fires r = Number of fires Cumulative precip. Temperature Relative humidity Precipitation Fire size Wind speed Relative humidity Temperature Burned Area (1 3 acre) 6 4 Santa Ana fires r = Number of fires # Santa Ana events Cumulative precip. Wind speed Relative humidity Fire size Wind speed Relative humidity

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29 Moritz et al., 1 Climatic controls

30 Fire interannual variation: region Precipitation PDSI, climate region Water Year PCP Water Year cumu Winter PDSI Spring Summer Fall

31 WRF Historical run forced with NARR (1981 ) Creation of WRF Future Boundary Conditions: Monthly ΔGCM Files = CCSM4 (41 6) CCSM4 (1981 ) 3 hrly NARR (1981 ) + ΔCCSM4 (linearly interpolated between monthly values)

32 Sat>6m/s Composite Wind Speed Map (1981 )

33 Sat>1m/s Composite Wind Speed Map (1981 )