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Tracking Variation in California’s Santa Ana Winds to Improve Fire-Risk Modeling

Photo of The 2017 Thomas Fire in southern California spread quickly, driven by 80 mph Santa Ana winds.The 2017 Thomas Fire in southern California spread quickly, driven by 80 mph Santa Ana winds.Snapshot : With a topography marked by mountain passes and canyons, fire behavior is challenging to predict in southern California, particularly when driven by strong Santa Ana winds. Scientists analyzed wind speed and direction—critical information for predicting fire spread—on days when fires ignite, both during Santa Ana and non-Santa Ana conditions. They also identified geographic gaps in the meteorological station network where strategic placement of additional stations would provide information useful to predicting fire risk.

Principal Investigators(s) :
Kim, John 
Research Location : California
Research Station : Pacific Northwest Research Station (PNW)
Year : 2020
Highlight ID : 1667

Summary

The Santa Ana winds are notorious in southern California for their role in spreading large wildfires during the fall/winter season. Combined with southern California's complex topography, Santa Ana winds create challenges for modeling wind-fire relationships in the region. Working with colleagues, USDA Forest Service scientist John B. Kim, assessed the spatial heterogeneity of winds during Santa Ana and non-Santa Ana days, on days with and without large-fire ignitions, across a modern high-density observational network of 30 meteorological stations. They found that wind speeds on Santa Ana days with a large fire ignition (mean windspeed = 5.19 m/s) are significantly higher than on Santa Ana days without large fire ignitions (3.96 m/s), On non-Santa Ana days winds are generally weaker, during both fire (2.30 m/s) and non-fire (2.38 m/s) days. They also identified five meteorological stations that are positioned to meet the geographic criteria for use in fire simulation models. Their analysis revealed that key geographic siting traits are not represented in the network, including few stations with northwest aspect and upper slope in the southern mountains. The study provides a template that fire modelers can use to select observational data appropriate to their purpose.

Forest Service Partners

External Partners

  • Karin Riley, Rocky Mountain Research Station
  •  Western Wildland Environmental Threat Assessment Center