Several storms that California has experienced are adding moisture to the ground and bringing more fog events than in previous winters. UC Cooperative Extension Orchard Systems Advisor for Yolo, Solano, and Sacramento counties, Kat Jarvis-Shean said conditions have helped bring back foggier weather that used to be much more frequent in California.
“I would say that just anecdotal experience from up here around where I am, even the early storms that we got, we seemed to go into the winter with a fair amount of moisture around and in the soil,” Jarvis-Shean noted. “So, it has seemed like a foggier winter to me than what we’ve gotten in recent years. It feels more like the foggy winters of my childhood in Yolo County.”
The amount of foggy conditions California has experienced in recent years is significantly different than what was seen 20 years ago. A study that was published back in 2014 found that fog events specifically in the Central Valley decreased by approximately 46 percent since 1981. Similar declines in foggy conditions have also been noted in multiple areas of California, impacting chill conditions for agricultural production.
Foggy conditions affect chill accumulation by shrouding trees from direct sunlight. Trees will not intercept as much solar radiation through a fog layer, in turn preventing them from heating up during the day. “When they’re out lying in the sunshine, they get a lot warmer than the ambient air temperature. Whereas if they’re not exposed to the sunshine like that because they’re in foggy conditions, they don’t get heated up as much,” Jarvis-Shean explained.
Information from the UC Davis Chill Calculator shows that as of January 18, the Durham CIMIS station has logged 53.5 portions under the dynamic model, with 884 hours below 45°F. The station in Manteca has registered 50.8 portions, with 798 hours. There have been 923 hours in Merced, with 51.7 cumulative portions. In Five Points, there have been 861 chill hours, equating to 48.5 portions. Finally, the CIMIS station in Shafter has registered 47.5 portions, with 851 hours.
Listen to the latest chill report below.