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Chapter 7: Precipitation Change in the United StatesAnnual precipitation has decreased in much of the West, Southwest, and Southeast and increased in most of the Northern and Southern Plains, Midwest, and Northeast. A national average increase of 4% in annual precipitation since 1901 is mostly a result of large increases in the fall season. Heavy precipitation events in most parts of the United States have increased in both intensity and frequency since 1901. There are important regional differences in trends, with the largest increases occurring in the northeastern United States. In particular, mesoscale convective systems (organized clusters of thunderstorms)-the main mechanism for warm season precipitation in the central part of the United States-have increased in occurrence and precipitation amounts since 1979. The frequency and intensity of heavy precipitation events are projected to continue to increase over the 21st century (high confidence). Mesoscale convective systems in the central United States are expected to continue to increase in number and intensity in the future. There are, however, important regional and seasonal differences in projected changes in total precipitation: the northern United States, including Alaska, is projected to receive more precipitation in the winter and spring, and parts of the southwestern United States are projected to receive less precipitation in the winter and spring. Northern Hemisphere spring snow cover extent, North America maximum snow depth, snow water equivalent in the western United States, and extreme snowfall years in the southern and western United States have all declined, while extreme snowfall years in parts of the northern United States have increased. Projections indicate large declines in snowpack in the western United States and shifts to more precipitation falling as rain than snow in the cold season in many parts of the central and eastern United States.
Document ID
Acquisition Source
Goddard Space Flight Center
Document Type
Book Chapter
External Source(s)
Easterling, D. R.
(National Climatic Data Center Asheville, NC, United States)
Kunkel, K. E.
(North Carolina State Univ. Raleigh, NC, United States)
Arnold, J. R.
(Corps of Engineers Alexandria, VA, United States)
Knutson, T.
(National Oceanic and Atmospheric Administration Princeton, NJ, United States)
LeGrande, A. N.
(NASA Goddard Inst. for Space Studies New York, NY, United States)
Leung, L. R.
(Pacific Northwest National Lab. Richland, WA, United States)
Vose, R. S.
(National Climatic Data Center Asheville, NC, United States)
Waliser, D. E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Wehner, M. F.
(California Univ. Berkeley, CA, United States)
Date Acquired
February 20, 2018
Publication Date
January 1, 2017
Publication Information
Publication: Climate Science Special Report: Fourth National Climate Assessment
Publisher: U.S. Global Change Research Program
Volume: I
Subject Category
Meteorology And Climatology
Report/Patent Number
Funding Number(s)
Distribution Limits
Use by or on behalf of the US Gov. Permitted.
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