Dryer, warmer night air is making some Western wildfires more active at night
Firefighters have reported that Western wildfires are starting earlier in the morning and dying down later at night, hampering their ability to recover and regroup before the next day’s flareup.
The research study calculated the percent change from the ’80s and ’90s to the 2010s in the nighttime vapor pressure deficit, a measure of the drying power of the air, during summer months. Nighttime conditions were much more conducive to drying in recent years, especially in California’s central valley and the Bitterroot-Blue Mountain region of Idaho and surrounding states. Chiodi et al. 2021/Geophysical Research Letters
Focusing on the two areas with the biggest change in nighttime air — the Northern Rockies (orange line at top) and the southern Sierra Nevada (orange line at bottom) — shows much bigger changes in summer nighttime vapor pressure deficit than the average across the West (green line). The study finds a link between the average value across the West and the Pacific Decadal Oscillation, a long-term climate pattern shown in the inset.
