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An Evaluation of Teleconnections Over the United States in an Ensemble of AMIP Simulations with the MERRA-2 Configuration of the GEOS Atmospheric ModelThe atmospheric general circulation model that is used in NASA's Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) is evaluated with respect to the relationship between large-scale teleconnection patterns and daily temperature and precipitation over the United States (US) using a ten-member ensemble of simulations, referred to as M2AMIP. A focus is placed on four teleconnection patterns that are known to influence weather and climate in the US: El Nino Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation, and the Pacific-North American Pattern. The monthly and seasonal indices associated with the patterns are correlated with daily temperature and precipitation statistics including: (i) monthly mean 2 m temperature and precipitation, (ii) the frequency of extreme temperature events at the 90th, 95th, and 99th percentiles, and (iii) the frequency and intensity of extreme precipitation events classified at the 90th, 95th, and 99th percentiles.Correlations obtained with M2AMIP data and thus the strength of teleconnections in the free-running model are evaluated through comparison against corresponding correlations computed from observations and from MERRA-2. Overall, the strongest teleconnections in all datasets occur during the winter and coincide with the largest agreement between the observations, MERRA-2, and M2AMIP. When M2AMIP does capture the correlation seen in observations, there is a tendency for the spatial extent to be exaggerated. The weakest agreement between the data sources, for all teleconnection patterns, is in the correlation with extreme precipitation; however there are discrepancies between the datasets in the number of days with at least 1 mm of precipitation: M2AMIP has too few days with precipitation in the Northwest and the Northern Great Plains and too many days in the Northeast. In JJA, M2AMIP has too few days with precipitation in the western two-thirds of the country and too many days with precipitation along the east coast.
Document ID
20180001607
Document Type
Technical Memorandum (TM)
Authors
Collow, Allison B. Marquardt (Universities Space Research Association Columbia, MD, United States)
Mahanama, Sarith P. (Science Systems and Applications, Inc. Lanham, MD, United States)
Bosilovich, Michael G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Koster, Randal D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Schubert, Siegfried D. (Science Systems and Applications, Inc. Lanham, MD, United States)
Date Acquired
March 5, 2018
Publication Date
May 1, 2017
Subject Category
Meteorology and Climatology
Report/Patent Number
NASA/TM-2017-104606/VOL47
GSFC-E-DAA-TN43904
Funding Number(s)
CONTRACT_GRANT: NNG17HP01C
CONTRACT_GRANT: NNG11HP16A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
JJA
M2AMIP
Great Plains

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