California’s later, sharper rainy season means more wildfires, debris flows

[Rex Sanders]

LA Times: California’s rainy season is starting about a month later than it did in the 1960s, researchers say
https://www.latimes.com/california/story/2021-02-13/californias-rainy-season-is-starting-about-a-month-later-than-it-did-in-the-1960s-researchers-say

Our rainy season now starts 27 days later than 60 years ago, with most rain and snow concentrated in a couple of winter months, and less in the fall and spring.

Also, strong offshore winds in the late fall (“Santa Ana” and “Diablo” winds) coming at the end of a longer, dryer summer, means worse and more frequent wildfires in October and November.

In “the annual race between the rain and the Santa Ana winds,” the rain is losing.

And more wildfires followed by more intense rains means more debris flows (basically fast moving mudslides).

Besides wreaking havoc on rural communities, urban water supplies, and farming, these changes make backpacking in California much more challenging.

Altered weather patterns also mean more rain and snow in Washington, Oregon, and probably British Columbia.

Journal article: https://doi.org/10.1029/2020GL090350

Climate change: It’s going to be a wild ride!

— Rex

[JB]

Additionally, warmer temperatures means that more of the precipitation that falls on the Sierra Nevada falls as rain instead of snow with higher freezing lines, meaning less water storage into the summer in the snowpack, and peak inflow into reservoirs happening earlier.

CA has a (geologically) recent history of 75-150 year droughts severe enough that Tenaya lake was empty and 80ft tall trees grew up in it, so climate change or not, things could get pretty bad pretty quick.

[Author]

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