Is climate change to blame for the atmospheric rivers impacting California? The evidence says “No.”
By
Chris Martz
|
March 17th, 2024
Since the end of January, California has been pelted by a series of atmospheric rivers bringing rounds of moderate-to-heavy rainfall for days on end, spurring hundreds of flash floods across the state, inundating roads and neighborhoods from the Bay Area to Los Angeles, and triggering several destructive mudslides. Each event has been separated only by a brief lull, providing Californians little relief from the deluge. Additionally, heavy upslope mountain snow in the Sierra Nevada has brought California’s snowpack—measured as snow water content—up to 104% of the 1970 to 2022 historical median (Figure 1) as of March 4th.[1]
Figure 1. California snow water content vs historical (1970-2022) percentiles. Source: Engaging Data.
The Meteorology
The recent boost in Sierra snowpack over the last few days was actually driven by a deep low-pressure area that originated in the Gulf of Alaska and then transcended down the Pacific coastline and into the Pacific Northwest. Pressure falls in the extratropical cyclone’s center increased the low-level convergence field, allowing the system to tap into the Pacific moisture and steer it inland through advection. Upon coming into contact with sloped terrain on the windward side of the Sierra Nevada, the moisture-enriched air was force-lifted up the mountain, whereby it was dynamically cooled to saturation, at which point the vapor could condense and precipitate back down into subfreezing air at elevations above 5,000 feet. Persistently heavy snow accompanied by >90 mph wind gusts prompted the National Weather Service (NWS) to issue blizzard warnings from last Thursday, February 29th, to Sunday, March 3rd, for the ski areas.
Within the last 60 days alone, large portions of Central and Southern California have received 200-300% of normal precipitation (Figure 2), as measured relative against 1991 to 2020 climatology.[2] Los Angeles recorded their fourth wettest February on record since 1878, with 12.66 inches of rainfall (more than three times their monthly average for February), and third largest two-day rainfall total of 7.03 inches ending on February 5th, only behind January 25-26th, 1956 (7.44 inches) and December 31st, 1933-January 1st, 1934 (7.98 inches).
https://www.cfact.org/2024/03/17/is-climate-change-to-blame-for-the-atmospheric-rivers-impacting-california-the-evidence-says-no/?utm_source=rss&utm_medium=rss&utm_campaign=is-climate-change-to-blame-for-the-atmospheric-rivers-impacting-california-the-evidence-says-no&utm_source=rss&utm_medium=rss&utm_campaign=is-climate-change-to-blame-for-the-atmospheric-rivers-impacting-california-the-evidence-says-no
