September 29th, 2025
Key Findings
- Santa Ana Winds (SAWs) are powerful, episodic winds blowing from the interior of the western US to coastal areas in Southern California, primarily in the Fall and WInter seasons. These hot, dry winds create enhanced risk of wildfires.
- The new high-resolution version of the GFDL SPEAR model (25 km horizontal grid) is able to more realistically simulate the SAWs than lower resolution versions (100 Km, 50 Km). The high-resolution model is able to better represent the complex topography of Southern California that is crucial for generating the characteristics of SAWs.
- In a future climate with global warming, SAWs are projected to become less frequent, due in part to more rapid warming of the interior regions than coastal areas.
- Despite occurring less frequently, the SAWs simulated in the high-resolution model are projected in the future to lead to even more extreme drying and warming near the surface in SAW events, thereby elevating the future risk of wildfires from SAW events. This aspect is not captured at lower model resolutions.
Yujia You, Thomas L. Delworth. Geophysical Research Letters. DOI: 10.1029/2025GL114994
Santa Ana winds (SAWs) are hot and dry winds that blow from the Great Basin (Nevada and adjacent areas) to coastal Southern California. SAW events usually last several days, and occur in Fall and WInter (see upper left panel of Figure). These hot, dry winds increase the likelihood and intensity of wildfires and their associated damage. Predicting how these winds will change in the future is challenging because most current-generation climate models struggle to simulate SAWs accurately.
The authors examined how varying horizontal grid spacings (100, 50, and 25 km) used in GFDL’s SPEAR climate model affect the simulation and future projection of SAWs. At high resolution (25 km grid) the model more accurately resolves SAWs and their intense winds than at the lower resolutions (100 km) commonly used in many models. The high resolution model better represents coastal mountain ranges, which improves the simulation of SAWs by intensifying the land-sea temperature contrasts and more realistically simulating the flow of air from the elevated interior regions through mountain ranges and eventually descending to the lower elevation of the coastal regions. As a result, the occurrence and intensity of SAWs at 25-km resolution are more realistic compared to coarser resolutions. The changes in SAW related saturation vapor pressure (how much moisture the air can hold) are more realistically simulated in the high resolution version than at lower resolution (see Figure, contrasting panels b, c, and d).
Using the high-resolution version of SPEAR, the authors investigate the response of SAWs to global warming. The results show a robust decrease in SAW frequency with climate warming, consistent with prior work. However, the high resolution simulations show that SAW events in a warmed world create significantly more drying and warming than is seen with lower resolution models. These results, only revealed with the high-resolution model, suggest that future SAWs in a warmed world could pose a greater wildfire risk to coastal Southern California.
The role of SAWs in exacerbating wildfires, damaging infrastructure, and affecting public health makes them a major concern for residents, businesses, and government agencies. Understanding and predicting their effects is crucial for minimizing the risks they pose to both human lives and the environment. The resolution of the GFDL model used in this study is higher than that of most current-generation models involved in the Coupled Model Intercomparison Project Phase 6. This research aligns with NOAA’s goal of detecting changes in the ocean and atmosphere and improving forecast accuracy.
