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Keith Oleson

understanding urban effects on climate and weather (e.g., as reviewed by Landsberg 1981 ; Oke 1988 ; Arnfield 2003 ; Collier 2006 ; Seto and Shepherd 2009 ). The urban heat island (UHI), a phenomenon describing the fact that urban areas are generally warmer than the surrounding rural areas was first recognized by Luke Howard in 1820 as described by Landsberg (1981) in his authoritative review of the field of urban climatology ( Oke 1991 ). The causes of the UHI were investigated in a series of

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David M. Lawrence, Keith W. Oleson, Mark G. Flanner, Christopher G. Fletcher, Peter J. Lawrence, Samuel Levis, Sean C. Swenson, and Gordon B. Bonan

are introduced in section 2 . In section 3 , we present an assessment of the surface climate simulation in CCSM4 with a focus on variables such as surface air temperature, precipitation, soil water storage, evapotranspiration, river discharge, and surface albedo as well as an assessment of the snow albedo feedback. In section 4 , we highlight results that emphasize several new earth system capabilities in CLM4. Specifically, we examine the urban heat island derived from the CLM4 urban canyon

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

present-day insolation to the insolation of 115 000 years ago (115 kya). Section 3 then analyzes in detail the Arctic heat budget with its multitude of positive and negative feedbacks, and section 4 analyzes the reorganization of the Atlantic meridional overturning circulation (AMOC). Section 5 concludes the study with a summary and implications for future model development. The two main goals of the present work are to demonstrate that the 115-kya orbital changes produce a realistic increase in

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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

of different spinup procedures used in CCSM3 and CCSM4 to obtain initial conditions for the 20C simulations ( Gent et al. 2011 ). The CCSM3 strategy was to obtain a relatively well-balanced top of the atmosphere model (TOA) heat flux in the present-day control integration. The 1870 preindustrial control used the same tuning. The 20C ensemble members subsequently started from various stages of this 1870 control. In contrast, with the CCSM4 simulations, the objective was to get a well-balanced TOA

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C. Kendra Gotangco Castillo, Samuel Levis, and Peter Thornton

–stem area index (LAI, SAI, respectively), and canopy height. In CNDV, the gap mortality calculation includes heat stress and growth efficiency considerations from the corresponding DGVM algorithm (section 2.8 in Levis et al. 2004 ). All other ecosystem processes (allocation, phenology, fire, etc.) are handled by CN (more details in Oleson et al. 2010 ). Including the nitrogen cycle in the CLM has been shown to dampen the response of land–atmosphere carbon exchange to climate variability as the

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Alexandra Jahn, Kara Sterling, Marika M. Holland, Jennifer E. Kay, James A. Maslanik, Cecilia M. Bitz, David A. Bailey, Julienne Stroeve, Elizabeth C. Hunke, William H. Lipscomb, and Daniel A. Pollak

and exist mainly in the form of climatological fields along cruise tracks and of mooring data that generally do not span more than 10 yr. Consequently, we cannot assess how well the CCSM4 captures the temporal variability of oceanic properties in the Arctic Ocean. We can, however, use the climatological fields and the various flux measurements reported in the literature to establish how well the CCSM4 captures the climatological features of the Arctic water masses and the volume, heat, and

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Gerald A. Meehl, Julie M. Arblaster, Julie M. Caron, H. Annamalai, Markus Jochum, Arindam Chakraborty, and Raghu Murtugudde

: Monsoon breaks and subseasonal sea surface temperature variability in the Bay of Bengal . J. Climate , 15 , 1485 – 1493 . Vranes , K. , A. L. Gordon , and A. Ffield , 2002 : The heat transport of the ITF and implications for the Indian Ocean heat budget . Deep-Sea Res. II , 49 , 1391 – 1410 . Wajsowicz , R. C. , 1993 : The circulation of the depth-integrated flow around an island with application to the Indonesian Throughflow . J. Phys. Oceanogr. , 23 , 1470 – 1484 . Waliser , D

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Gijs de Boer, William Chapman, Jennifer E. Kay, Brian Medeiros, Matthew D. Shupe, Steve Vavrus, and John Walsh

surface wind speed and direction, temperature, and precipitation. Wind speed and direction are particularly important in the Arctic for advection of simulated sea ice ( DeWeaver and Bitz 2006 ) and governance of heat fluxes between the ocean–land surface and atmosphere. Chapman and Walsh (2007) also evaluated simulated Arctic SLP. In general, ESM-simulated storm tracks were demonstrated to be shorter than those observed, with observed storms often reaching the Kara Sea and simulated storm tracks

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

been paid recently to potential “switches” between modes having centers of action in the eastern and central Pacific ( Kao and Yu 2009 ; Yeh et al. 2009 ). And indeed physical changes to the tropical Pacific, such as alterations of heat content or the structure of the wind stress curl, must necessarily impact ENSO and the tropical heat budget—eventually. But understanding how and when that impact might be realized is not often discussed in the context of coupled model results. This paper will show

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

. The twentieth-century warming is overestimated in relation to the instrumental record, and is comparable to all CCSM4 twentieth-century simulations, which show too large a rate of heat gain after 1970 ( Meehl et al. 2012 ). Much of this overestimation of heat gain is consistent with CCSM4 not including the negative forcing because of indirect effects of aerosols ( Gent et al. 2011 ; Meehl et al. 2012 ). The equilibrium climate sensitivity of CCSM4 is 3.2°C, in the middle of the range of the CMIP3

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