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Summary: GEOPHYSICAL RESEARCH LETTERS, VOL. 27, NO. 4, PAGES 565-568, FEBRUARY 15, 2000
The North American monsoon system in the
Hadley Centre coupled ocean-atmosphere GCM
Raymond W. Arritt, Dustin C. Goering and Christopher J. Anderson
Iowa State University, Ames
Abstract. The North American monsoon system (NAMS)
as represented in the second-generation Hadley Centre cou-
pled ocean-atmosphere model is examined using high-time-
resolution (six-hourly) records of model output. A current-
climate simulation gives a realistic depiction of the NAMS,
with date of onset and precipitation trends agreeing with ob-
servations. The model reproduces the observed negative re-
lationship between precipitation over the southwestern U.S.
and that over the central U.S. Changes in tropospheric cir-
culation and moisture after onset are consistent with ob-
served changes although mid-level moistening is less than
is observed. An enhanced greenhouse-gas simulation gives
higher precipitation and stronger tropospheric dynamical
and moisture changes after onset.
Introduction
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