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K. J. Evans, P. H. Lauritzen, S. K. Mishra, R. B. Neale, M. A. Taylor, and J. J. Tribbia

Hemisphere midlatitudes and to a lesser degree the North Atlantic storm tracks, an issue that has been present in the CAM, version 3, where it is attributed to underestimated gravity wave drag in the mountain stress contribution to the balanced atmospheric momentum flux ( Collins et al. 2006 ). CAM-SE values are higher than CAM-FV and are significantly further from observations in that region, suggesting that the gravity wave drag is too weak in CAM-SE, due to CAM-SE’s use of smoother topography. Fig

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Shih-Yu Wang, Michelle L'Heureux, and Jin-Ho Yoon

: The North Pacific Oscillation . Int. J. Climatol. , 1 , 39 – 57 . Roundy , P. E. , and G. N. Kiladis , 2007 : Analysis of a reconstructed oceanic Kelvin wave dynamic height dataset for the period 1974–2005 . J. Climate , 20 , 4341 – 4355 . Schmidt , G. A. , and Coauthors , 2006 : Present-day atmospheric simulations using GISS ModelE: Comparison to in situ, satellite and reanalysis data . J. Climate , 19 , 153 – 192 . Smith , T. M. , R. W. Reynolds , T. C. Peterson , and

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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

2008 ), the pan-Pacific mode ( Guan and Nigam 2008 ), and the North Pacific gyre oscillation ( Di Lorenzo et al. 2008 ). Investigation of these additional patterns in the Community Climate System Model version 4 (CCSM4) is beyond the scope of this study. Various mechanisms have been hypothesized to account for PDV, including ENSO and associated atmospheric teleconnections to the North Pacific, forcing by random fluctuations in the Aleutian low pressure system, oceanic Rossby wave adjustment to wind

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Semyon A. Grodsky, James A. Carton, Sumant Nigam, and Yuko M. Okumura

atmospheric model component. This paper revisits the problem of biases in coupled simulations of the tropical Atlantic through examination of the Community Climate System Model, version 4 (CCSM4; Gent et al. 2011 ), a coupled climate model simultaneously simulating the earth’s atmosphere, ocean, land surface, and sea ice processes. The predominant feature of the seasonal cycle of the tropical Atlantic is the seasonal meridional shift of the zonally oriented intertropical convergence zone (ITCZ), which

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Richard B. Neale, Jadwiga Richter, Sungsu Park, Peter H. Lauritzen, Stephen J. Vavrus, Philip J. Rasch, and Minghua Zhang

potential (m 2 s −2 ) for (a),(b) ERA-40 and bias for (c),(d) CAM4 at 1°, (e),(f) CAM3 at T85, (g),(h) CCSM4 at 1°, and (i),(j) CCSM3 at T85. Atmospheric blocking and skill scores Recent observed extreme weather events have been linked to persistent continental high pressure blocking systems, both in summer [e.g., 2010 Russian heat wave; Dole et al. (2011) ] and winter [e.g., 2010 winter in northwestern Europe; Cattiaux et al. (2010) ]. For a model to reproduce these kinds of extreme events at any

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Laura Landrum, Marika M. Holland, David P. Schneider, and Elizabeth Hunke

” has corresponding anomalies in surface ocean characteristics and atmospheric fields. Additionally, work suggests that winter anomalies of sea ice are collocated with anomalies in sea surface temperature, sea level pressure, and wind stress and can propagate around the Antarctic continent ( White and Peterson 1996 ). The sea ice anomalies re-emerge from one year to the next because of an imprint of the winter ice conditions on the ocean surface temperatures ( Gloersen and White 2001 ). Variability

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Aneesh C. Subramanian, Markus Jochum, Arthur J. Miller, Raghu Murtugudde, Richard B. Neale, and Duane E. Waliser

A. M. Blyth , 1992 : Extension of the stochastic mixing model to cumulonimbus clouds . J. Atmos. Sci. , 49 , 1968 – 1983 . Richter , J. , and P. J. Rasch , 2008 : Effects of convective momentum transport on the atmospheric circulation in the Community Atmosphere Model, version 3 . J. Climate , 21 , 1487 – 1499 . Roundy , P. , 2008 : Analysis of convectively coupled Kelvin waves in the Indian Ocean MJO . J. Atmos. Sci. , 65 , 1342 – 1359 . Roundy , P. , and J. R. Kravitz

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Samantha Stevenson, Baylor Fox-Kemper, Markus Jochum, Richard Neale, Clara Deser, and Gerald Meehl

result, two separate but inextricably linked questions arise: what are the main dynamical controls on ENSO amplitude in future climates? And perhaps even more importantly, when can a change in ENSO amplitude be distinguished from natural variability? This study is intended to provide a look at the climate change–ENSO link from a statistical perspective, from which the reliability and relevance of dynamical changes can be understood. Here, the new version of the National Center for Atmospheric

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Kevin Raeder, Jeffrey L. Anderson, Nancy Collins, Timothy J. Hoar, Jennifer E. Kay, Peter H. Lauritzen, and Robert Pincus

available DA algorithms. That effort has been greatly reduced by the advent of ensemble DA, so that climate model development and research can now benefit greatly and directly from the variety of tools available from DA. Several generations of the Community Atmosphere Model [CAM, the atmospheric component of the Community Earth System Model (CESM)] can now be used with ensemble DA using the Data Assimilation Research Testbed (DART). The DART algorithm and software are described briefly here ( section 2

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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

) simulations in comparison with available observations and those of CCSM3, presenting improvements as well as existing biases in CCSM4; and iii) to assess the consequences of two different spinup procedures used in CCSM3 and CCSM4 on the deep ocean properties. In addition, the solutions from an ocean–sea ice hindcast case forced with interannually varying atmospheric data are documented in comparison with observations as well as the 20C simulations, the former to assess the fidelity of the forced ocean

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