Precipitation differences amongst GCMs used for the U.S. national assessment

• Published in: Journal of the American Water Resources Association
• Other Authors: Felzer, Benjamin (Benjamin Felzer) (authoraut), Heard, Preston (Preston S. Heard) (authoraut)
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons
• Subjects: Pacific; aleutian low
• Online Access: https://doi.org/10.1111/j.1752-1688.1999.tb04218.x; http://n2t.net/ark:/85065/d7pn96q6

Two general circulation models (GeMs) used in the U.S. national assessment of the potential consequences of climate variability and change (CGCMl and H adCM2) show a large increase in precipitation in the future over the southwestern U.S., particularly during winter. This precipitation increase is an extension of a larger region of increased precipitation in the Pacific Ocean off the west coast or North American that is associated with a deepened and southward-shifted Aleutian Low, a weaker subtropical high, and wanner sen surface temperatures (SSTs). The models differ in their simulation of precipitation anomalies over the southeastern U.S., with CGCM1 showing drier conditions and HadCM2 showing wetter conditions in the future. While both models show decreased frequency of Atlantic storms, consistent with decreased meridional and land/sea temperature gradients, the more coastal position of the storm track in CGCM1 results in less precipitation than modern along the eastern seaboard of the U.S. During summer, differences in land surface models within the two GCMs sometimes lead to differences in soil moisture that feed back to the precipitation over land due to available moisture.