Don't have time to get into the nitty-gritty of the details today, but here's the gist: a team of researchers at UCLA led by Professor Alex Hall is reporting that anthropogenic global warming is reducing by about one-third the pressure in the Great Basin that builds every year and leads to dangerous Santa Ana wind conditions.
As the pressure gradually decreases, the frequency and intensity of these winds is decreasing as well. Santa Ana winds depend on a build up of high pressure systems over the Great Basin in eastern California, Nevada, and Utah in fall and sometimes in winter. This pressure builds and is drawn towards low pressure systems over the ocean off Los Angeles. But as the land warms, fewer icy desert nights reduce the difference in temperature between the air over the desert and the air over the ocean. This inhibits the production of the most powerful of these hot, blustery winds.
The risk is not eliminated — as the Porter Ranch fire this week shows — but Hall's team says the research "suggests the reduction in the frequency [of Santa Ana winds] could lead to reduced wildfire in Southern California."
Here's a link to a page where the study is available, under the title Anthropogenic Reduction of Santa Ana Winds.
More soon in the VC Reporter. For now, take a look at a chart at a declining trend (the black dotted line) in the high pressure on its home turf in the Great Basin during the Santa Ana season over the past several decades, a trend the researchers are confident will continue to strengthen.
(Admittedly, one could cherry-pick a very different and much more ominous trend-line, from the low in l982 to a high in 2003, but that would fly in the face of what the physics projects.)
Kit Stolz 