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Samuel Levis, Gordon B. Bonan, Erik Kluzek, Peter E. Thornton, Andrew Jones, William J. Sacks, and Christopher J. Kucharik

have explored the effects of human land use on the earth system by usually replacing trees in land surface models with a simplistic representation of crops, such as grasses ( Pitman et al. 2009 ). However, realistic crop phenology and the use of fertilizer and irrigation give croplands different biogeophysical and biogeochemical characteristics relative to grasslands. Xue et al. (1996) reduced North American temperature biases in their coupled land–atmosphere model by prescribing more appropriate

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Synte Peacock

by Gent et al. 2011 . A discussion of future global projected changes out to the year 2300 for the four RCP emissions scenarios can be found in Meehl et al. 2012 . This paper focuses on the simulated temperature, precipitation, and snow cover changes over North America. Model bias in late twentieth-century temperature, precipitation, and snow cover is presented, in addition to bias-corrected projections and projected changes in these fields over the twenty-first century. 2. Model description

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Kerry H. Cook, Gerald A. Meehl, and Julie M. Arblaster

1. Introduction In this paper we document the West African, East African, North American, and South American monsoon regimes and associated processes for the Community Climate System Model, version 4 (CCSM4). This is the second of a two part series, with the first part ( Meehl et al. 2012 , hereafter Part I ) studying the Asian–Australian monsoon in CCSM4. Output from the fully coupled CCSM4 simulation is compared to the atmosphere-only the Community Atmosphere Model, version 4 (CAM4) runs

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Laura Landrum, Bette L. Otto-Bliesner, Eugene R. Wahl, Andrew Conley, Peter J. Lawrence, Nan Rosenbloom, and Haiyan Teng

simulations confirm that volcanic forcing has induced a positive winter NAO response over northern Europe the first two winters after an eruption ( Fischer et al. 2007 ), decadal-length annual and late winter (February–March) cooling over western (especially interior) North America ( Wahl and Ammann 2010 ), and multidecadal variability of North Atlantic SSTs ( Otterå et al. 2010 ). The purpose of this paper is to provide an overview of the Last Millennium simulation of the Community Climate System Model

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Clara Deser, Adam S. Phillips, Robert A. Tomas, Yuko M. Okumura, Michael A. Alexander, Antonietta Capotondi, James D. Scott, Young-Oh Kwon, and Masamichi Ohba

, and off the west coast of North America ( Fig. 1 ). However, the magnitudes of õ SST in CCSM4–1° are approximately 30% stronger than observed in all 3 regions. In comparison, õ SST in CCSM4–2° is overestimated by at least 70% in these areas. Values of õ SST in CCSM3–T85 are comparable to those in CCSM4–1° over the North Pacific and more realistic than those in CCSM4–1° over the equatorial cold tongue. Fig . 1. Climatological annual mean SST (contoured every 2°C beginning at 5°C; the thick

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Peter J. Lawrence, Johannes J. Feddema, Gordon B. Bonan, Gerald A. Meehl, Brian C. O’Neill, Keith W. Oleson, Samuel Levis, David M. Lawrence, Erik Kluzek, Keith Lindsay, and Peter E. Thornton

use any natural vegetation grown in an area (e.g., pastoral herding practices as used in Africa or Mongolia, or rangeland grazing in Australia). The historical CMIP5 time series suggests that the pasture land unit applies to both of these definitions, as there are very intensive pasture values in very sparsely vegetated parts of the world that cannot be considered equivalent to the intensive grazing of the lush pastoral grass fields of Europe or North America. To address these definitional

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Gokhan Danabasoglu, Susan C. Bates, Bruce P. Briegleb, Steven R. Jayne, Markus Jochum, William G. Large, Synte Peacock, and Steve G. Yeager

improvements are largely due to the different spinup procedure used in CCSM4 than in CCSM3—as detailed in Gent et al. (2011) , the entire ocean, including SSTs, got colder in CCSM3 because of the significant heat loss in the preindustrial control simulation. Nevertheless, the large warm SST biases that originate in upwelling regions along the west coasts of North and South America and South Africa appear little changed in CCSM4 from CCSM3. Indeed, likely owing to the generally warmer SSTs in CCSM4, these

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Markus Jochum, Alexandra Jahn, Synte Peacock, David A. Bailey, John T. Fasullo, Jennifer Kay, Samuel Levis, and Bette Otto-Bliesner

Canada are too cold by about 1°C–2°C, and Baffin Island by about 5°C ( Gent et al. 2011 ). The Siberian biases are not so dramatic, but it is quite unfortunate that Baffin Island, the nucleus of the Laurentide ice sheet, has one of the worst temperature biases in CCSM4. A closer look at the temperature biases in North America, though, reveals that the cold bias is dominated by the fall and winter biases, whereas during spring and summer Baffin Island is too cold by approximately 3°C, and the Canadian

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Gokhan Danabasoglu, Steve G. Yeager, Young-Oh Kwon, Joseph J. Tribbia, Adam S. Phillips, and James W. Hurrell

over the ice-free oceans. As in the SST regressions, TS patterns for both indices are broadly similar, with both showing substantial warming over sea ice in the eastern Arctic and northern North Atlantic, general warming over North America, cooling over central Asia and in broad regions in Antarctica and warming to the west of the Antarctic Peninsula. These regression patterns suggest influences of global teleconnections associated with the AMV and AMOC PC1 time series. The simultaneous regressions

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Gretchen Keppel-Aleks, James T. Randerson, Keith Lindsay, Britton B. Stephens, J. Keith Moore, Scott C. Doney, Peter E. Thornton, Natalie M. Mahowald, Forrest M. Hoffman, Colm Sweeney, Pieter P. Tans, Paul O. Wennberg, and Steven C. Wofsy

using the same latitude–altitude bins. The second set of aircraft observations consisted of biweekly to monthly profiles sampled by the NOAA Global Monitoring Division and the U.S. Department of Energy (DOE) at 19 aircraft sites in the Northern Hemisphere, primarily over North America ( Fig. 1 ). Measurements were made between the surface and 8 km via automated portable flask packages aboard small aircraft. Table 3 lists the sites and the temporal coverage of the data. Like the surface flasks, the

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