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Title: Do climate model predictions agree with long-term precipitation trends in the arid southwestern United States?

item Elias, Emile
item Rango, Albert
item James, Darren
item Maxwell, Connie
item ANDERSON, JOHN - New Mexico State University
item ABATZOGLOU, JOHN - University Of Idaho

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 12/12/2016
Publication Date: 12/12/2016
Citation: Elias, E.H., Rango, A., James, D.K., Maxwell, C.J., Anderson, J., Abatzoglou, J. 2016. Do climate model predictions agree with long-term precipitation trends in the arid southwestern United States [abstract]? American Geophysical Union Fall Meeting. December 12-16, 2016, San Francisco, California.

Interpretive Summary:

Technical Abstract: Researchers evaluating climate projections across southwestern North America observed a decreasing precipitation trend. Aridification was most pronounced in the cold (non-monsoonal) season, whereas downward trends in precipitation were smaller in the warm (monsoonal) season. In this region, based upon a multimodel mean of 20 Coupled Model Intercomparison Project 5 models using a business-as-usual (Representative Concentration Pathway 8.5) trajectory, midcentury precipitation is projected to increase slightly during the monsoonal time period (July-September; 6%) and decrease slightly during the remainder of the year (October-June; -4%). We use observed long-term (1915-2015) monthly precipitation records from 16 weather stations to investigate how well measured trends corroborate climate model predictions during the monsoonal and non-monsoonal timeframe. Running trend analysis using the Mann-Kendall test for 15 to 101 year moving windows reveals that half the stations showed significant (p=0.1), albeit small, increasing trends based on the longest term record. Trends based on shorter-term records reveal a period of significant precipitation decline at all stations representing the 1950s drought. Trends from 1930 to 2015 reveal significant annual, monsoonal and non-monsoonal increases in precipitation (Fig 1). The 1960 to 2015 time window shows no significant precipitation trends. The more recent time window (1980 to 2015) shows a slight, but not significant, increase in monsoonal precipitation and a larger, significant decline in non-monsoonal precipitation. GCM precipitation projections are consistent with more recent trends for the region. Running trends from the most recent time window (mid-1990s to 2015) at all stations show increasing monsoonal precipitation and decreasing Oct-Jun precipitation, with significant trends at 6 of 16 stations. Running trend analysis revealed that the long-term trends were not persistent throughout the series length, but depended on the period examined. Recent trends in Southwest precipitation are directionally consistent with anthropogenic climate change.