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Bettina C. Lackner, Andrea K. Steiner, Gabriele C. Hegerl, and Gottfried Kirchengast

multisatellite climatologies. The anticipated climate change signal is estimated from an ensemble of anthropogenically forced scenario runs of three global climate models (GCM) of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC; Meehl et al. 2007 ). Natural variability is based on preindustrial control simulations of the same models. The focus region of our study is the UTLS within 50°S–50°N, where the best RO data quality is provided ( Steiner et al. 2009 ). A

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Michael Winton, Stephen M. Griffies, Bonita L. Samuels, Jorge L. Sarmiento, and Thomas L. Frölicher

% yr −1 CO 2 increase experiment. As noted in the introduction, simulated changes in ocean circulation are quite uncertain. In particular, some of the changes are known to be influenced by resolution. Farneti et al. (2010) show that eddy effects in a high-resolution simulation cancel much of the mean flow change in the southern ocean, an effect that was not well represented by GFDL CM2.1’s eddy parameterization ( Farneti and Gent 2011 ). b. Model results with fixed and free currents Figure 2

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Richard Seager, Alexandrina Tzanova, and Jennifer Nakamura

1. Introduction Perceptions of drought in North America normally focus on the arid and semiarid lands of the Great Plains and Canadian Prairies, the interior West, the Southwest, and Mexico. It might be thought that this focus is a consequence of the dryness of these regions: precipitation reductions of equal magnitude will create larger effects on water resources in dry regions than in the more humid regions of the Northwest, Southeast, and Northeast. But there is more to it than that

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Yiwen Xu, Bin Zhu, Shuangshuang Shi, and Yong Huang

. 2005 ). Ding et al. (2013) clarified the interaction between air pollution and weather conditions with five types. Li et al. (2015) quantified the effects of the aerosol–planetary boundary layer interaction and the aerosol–cloud–radiation interaction on weather conditions. A complex interaction was found between aerosols and atmospheric boundary layers; together, they determined the air pollution concentrations. The interaction between the boundary layer and aerosols and their feedback on other

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David P. Rowell and Robin Chadwick

1. Introduction Extremes of tropical rainfall, whether they are droughts or floods, can be catastrophic in developing countries. Poor infrastructure and a dependence on local agriculture leave vulnerable populations exposed. Over the coming decades, climate models predict that ongoing anthropogenic emissions will lead to sizable changes in the frequency, intensity, and spatiotemporal distribution of such events ( Collins et al. 2013 ). However, while these models provide confidence that many

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William Richard Hobbs, Nathaniel L. Bindoff, and Marilyn N. Raphael

scale and are robust to changes in the observing system ( Cavalieri et al. 1999 ; Parkinson and Cavalieri 2012 ). By contrast, most climate models driven by realistic natural and anthropogenic forcings simulate a significant decrease in Antarctic sea ice cover over the same period ( Turner et al. 2013 ; Fig. 1 ), and it is not clear whether the observed changes represent an externally forced change or multidecadal natural variability. Over the same period, coupled models replicate the observed

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Kevin E. Trenberth and John T. Fasullo

models and observations and methods used. Section 3 describes the main results relevant to the current observed climate for reanalyses and the climate models. Section 4 then delves into changes in energy-related quantities since 1950, relative to a base of 1900–50, and extending through the twenty-first century. Section 5 discusses the results and the conclusions are given in section 6 . The focus here is on aspects of the simulated budgets that are resilient both to the effects of problems in

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Zeng-Zhen Hu, Arun Kumar, Bhaskar Jha, and Bohua Huang

resolutions. The ocean model is the Parallel Ocean Program model with a horizontal resolution of 1° (down to 1/2° latitude in the equatorial tropics) and 40 vertical levels. No flux adjustments are used in CCSM3. There were two sets of experiments. One is referred to as A1B runs, which are forced by the SRES A1B scenario for the period January 2000–December 2061 with initial conditions (ICs) from a single simulation of twentieth-century climate (forced by a combination of anthropogenic and natural

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Paul W. Staten, Thomas Reichler, and Jian Lu

they do not directly address the realistic circulation response to anthropogenic climate forcings. Recently, studies have begun to address the ensemble-mean transient circulation response to switch-on climate forcings in complex general circulation models. For example, Wu et al. (2012) document the transient circulation response to a doubling of CO 2 , in the Community Atmosphere Model, version 3 (CAM3), coupled to a slab ocean. They suggest that the circulation response begins in the

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E. M. C. Demaria, E. P. Maurer, J. Sheffield, E. Bustos, D. Poblete, S. Vicuña, and F. Meza

where the underlying density of available station observations is low, the station locations are inadequate to represent complex topography, or where the gridded spatial resolution is too large for the region being studied. Central Chile is an especially challenging environment for characterizing climate and hydrology since the terrain exhibits dramatic elevation changes over short distances, and the orographic effects produce high spatial heterogeneity in precipitation. In general, the observation

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