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Assessment of Precipitation Anomalies in California Using TRMM and MERRA DataAfter more than a decade of moderate seasonal deviations from the expected climate, it is easy to forget that California is actually prone to instabilities in precipitation patterns that occur on various scales. Using modern satellite and reanalysis data we reassess certain aspects of the precipitation climate in California from the past three decades. California has a well-pronounced rain season that peaks in December-February. However, the 95% confidence interval around the climatological precipitation during these months imply that deviations on the order of 60% of the expected amounts are very likely during the most important period of the rain season. While these positive and negative anomalies alternate almost every year and tend to cancel each other, severe multi-year declines of precipitation in California seem to appear on decadal scales. The 1986-1994 decline of precipitation was similar to the current one that started in 2011, and is apparent in the reanalysis data. In terms of accumulated deficits of precipitation, that episode was no less severe than the current one. While El Niño (the warm phase of the El Niño Southern Oscillation, ENSO) is frequently cited as the natural forcing expected to bring a relief, our assessment is that ENSO has been driving at best only 6% of precipitation variability in California in the past three decades. It means El Niño needs to be stronger and longer, in order to have a higher likelihood of a positive impact, and the current one does not match these criteria. Using fractional risk analysis of precipitation populations during normal and dry periods, we show that the likelihood of losing the most intensive precipitation events drastically increases during the multi-year drying events. Since storms delivering up to 50% of precipitation in California are driven by atmospheric rivers making landfall, thus the importance of their suppression and blockage by persistent ridges of atmospheric pressure in the northeast Pacific.


Document ID
20190032009
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Savtchenko, Andrey K.
(Adnet Systems, Inc. Greenbelt, MD, United States)
Huffman, George
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Vollmer, Bruce
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
October 7, 2019
Publication Date
September 28, 2019
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN73845
Report Number: GSFC-E-DAA-TN73845
Meeting Information
Meeting: 2019 Joint Satellite Conference
Location: Boston, MA
Country: United States
Start Date: September 28, 2019
End Date: October 4, 2019
Sponsors: American Meteorological Society (AMS-HQ)
Funding Number(s)
CONTRACT_GRANT: 80GSFC17C0003
Distribution Limits
Public
Copyright
Public Use Permitted.
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