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Renu Joseph and Ning Zeng

–Southern Oscillation (ENSO) on vegetation and the carbon cycle ( Zeng et al. 2005 ; Qian et al. 2008 ). The model consists of the global version of the atmospheric model Quasi-equilibrium Tropical Circulation Model (QTCM) ( Neelin and Zeng 2000 ; Zeng et al. 2000 ), which simulates a reasonable seasonal climate compared to observations in the tropics and midlatitudes. The QTCM is coupled to the simple-land model ( Zeng et al. 2000 ), and a slab mixed layer ocean model with Q-flux to represent the effects of

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Alfredo Ruiz-Barradas and Sumant Nigam

. 2008 ); 2) NCAR’s Community Climate Model (CCM3) run by the Lamont-Doherty Earth Observatory group ( Kiehl et al. 1998 ; Seager et al. 2005 ); 3) the National Aeronautics and Space Administration Geophysical Fluid Dynamics Laboratory (NASA GSFC) Seasonal-to-Interannual Prediction Project (NSIPP-1) model ( Bacmeister et al. 2000 ; Schubert et al. 2004 ); 4) the NOAA–National Centers for Environmental Prediction’s (NCEP) Global Forecasting System (GFS) model ( Campana and Caplan 2009 ); and 5) the

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Bradfield Lyon

occurrence of these two climate extremes is of consequence in any region of the globe although research has largely focused on the two phenomena in isolation. In this paper, the occurrence of seasonal drought and heat waves is examined for the subcontinent of southern Africa (land areas south of 15°S). Observational characteristics of their behavior are first considered for the period 1961–2000 and then compared with related behavior in coupled models from the World Climate Research Programme’s (WCRP

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Alfredo Ruiz-Barradas and Sumant Nigam

obtained using the Hadley Centre’s Sea Ice and SST analysis that spans the time period from 1870 to 2002 on a 1° grid ( Rayner et al. 2003 ), but is used on a coarser 5° × 2.5° grid. Unless noted otherwise, climatology and long-term variability of the twentieth, twenty-first, and twenty-second centuries span the following 99-yr base periods: 1901–99, 2001–99, and 2101–99. To avoid intraseasonal variability, the basic data is seasonal and defined in terms of the typical 3-month means: December

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Rachel R. McCrary and David A. Randall

model. Unfortunately, with fully coupled simulations it is impossible to separate the effects of SST forcing and land–atmosphere interactions. One way to investigate the degree to which land–atmosphere interactions influence long-term drought might be to perform idealized SST experiments where global SSTs are set to the seasonally varying climatology. In these experiments, precipitation will only be influenced by internal atmospheric variability and land–atmosphere feedbacks, thus allowing us to see

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Randal D. Koster, Hailan Wang, Siegfried D. Schubert, Max J. Suarez, and Sarith Mahanama

above-mentioned connection between seasonally averaged evaporation and surface temperature, used the curve in Fig. 1 to interpret interannual variations in June–August (JJA) temperature averages in terms of the two evaporation regimes. Using both atmospheric general circulation model (AGCM) data and multidecadal precipitation and temperature observations, they showed that drier-than-average JJA conditions in regions characterized by soil moisture–controlled evaporation do indeed lead to positive

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Caio A. S. Coelho and Lisa Goddard

. Sections 4 and 5 examine how ENSO-induced drought patterns change in the twenty-first century and how such patterns can be combined with projected mean precipitation changes for estimating El Niño–induced drought risk in the twenty-first century. Section 6 concludes the manuscript with a summary and discussion of the findings. 2. Datasets and investigation approach El Niño precipitation teleconnections are reasonably well reproduced by seasonal climate models ( van Oldenborgh et al. 2005a

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Kingtse C. Mo, Jae-Kyung E. Schemm, and Soo-Hyun Yoo

1. Introduction Long-lasting drought has an enormous impact on the nation’s economy and society. Skillful drought prediction can mitigate devastating economic effects on people and ecosystems. To improve drought forecasts, one needs to understand the causes that trigger and sustain drought. Because drought implies prolonged rainfall and soil moisture deficits, they are often modulated by low-frequency sea surface temperature anomalies (SSTAs). In the Pacific, decadal trends of SSTAs in the

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Antonietta Capotondi and Michael A. Alexander

examined wind speeds and cold season (November–April) precipitation in the twentieth-century simulations of 18 models from the IPCC AR4 archive. They found that the model’s attenuation of orography over the Rocky Mountains is responsible for increasing the zonality of the atmospheric circulation, leading to faster wind speeds near 30°N and wet biases over western North America, as well as to a general distortion of the precipitation pattern. The seasonal evolution of precipitation is also very

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Philip J. Pegion and Arun Kumar

in the experiments were the NASA Seasonal-to-Interannual Prediction Program (NSIPP1) AGCM ( Bacmeister et al. 2000 ; Schubert et al. 2004a ), the NCAR Community Climate Model (CCM3) ( Kiehl et al. 1998 ; Seager et al. 2005 ), version 2.1 of the GFDL Atmospheric Model (AM2.1) ( Delworth et al. 2006 ; The GFDL Global Atmospheric Model Development Team 2004 ; Milly and Shmakin 2002 ), version 3.5 of the NCAR Community Atmosphere Model (CAM3.5), and the NCEP Global Forecast System (GFS) ( Campana

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