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Clark Weaver, Jay Herman, Gordon Labow, David Larko, and L.-K. Huang

1. Introduction Cloud radiative feedback quantifies an aspect of how clouds respond to a warming climate, specifically, the change in the top-of-atmosphere (TOA) reflected radiative flux from changes in cloud amount or morphology ( R cloud ) per degree temperature change at the earth’s surface. Here R cloud is called the cloud radiative forcing (watts per meter squared). Currently, the longest observational data record for shortwave (SW) R cloud is from the International Satellite Cloud

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Alan Condron, Peter Winsor, Chris Hill, and Dimitris Menemenlis

, toward a more neutral state after the mid-1990s. The direct response of the Arctic freshwater budget to the positive and negative phases of the NAO pattern were recently examined by Zhang et al. (2003) , and then by Houssais et al. (2007) , using regional coupled ocean–ice models of the Arctic, forced with NCEP data. To create atmospheric forcing fields for the NAO, the NCEP data were regressed onto the positive and negative phases of the NAO index over the last 50 years. Interestingly, even though

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Christopher B. Skinner, Moetasim Ashfaq, and Noah S. Diffenbaugh

predominant view among researchers largely attributes the variability of West African rainfall to changes in global sea surface temperatures, with localized land surface fluxes modulating the sea surface temperature forcing ( Zeng et al. 1999 ; Nicholson 2001 ; Giannini et al. 2003 ). Several studies have successfully reproduced the historical record of rainfall in the Sahel using climate models forced only with observed global SSTs (e.g., Giannini et al. 2003 ; Lu and Delworth 2005 ), and a number of

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Bjorn Stevens

1. Introduction A perturbation to the composition of Earth’s atmosphere can be quantified through the degree to which it disturbs the radiative balance at the top of the atmosphere, its radiative forcing. This radiative forcing is a motive force for climate change as (at least for small perturbations) Earth’s globally averaged surface temperature is expected to change proportionally with the forcing (e.g., Myhre et al. 2013a ; Sherwood et al. 2015 ). More than 20 years ago Charlson et al

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David A. Rahn and Thomas R. Parish

-dimensional context for aircraft observations at a particular point in space and time and are used here as a means to compare with the observational data on the structure and forcing of the CJ. Emphasis for the airborne study is placed on the direct measurement of the horizontal pressure gradient force (PGF) near the top of the MABL by the University of Wyoming King Air (UWKA) research aircraft. The fundamental idea behind measuring the PGF is to fly an instrumented aircraft along an isobaric surface. Heights are

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Takeaki Sampe and Shang-Ping Xie

circulation response in turn (e.g., Yamazaki and Chen 1993 ), so examining the observed convection or low-level circulation is not enough to elucidate the cause of the whole meiyu-baiu system. It is important to isolate the external forcing that anchors the climatological rainband. Fundamental questions remain unanswered: what determines the position and timing of the meiyu-baiu rainband? Why is convection active in the meiyu-baiu rainband while SST and surface equivalent potential temperature (cf. Figs

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Norman G. Loeb and Wenying Su

1. Introduction Radiative forcing by aerosols is identified as the largest uncertainty in anthropogenic radiative forcing of climate. Aerosols influence the radiation budget of the earth directly by scattering and absorbing solar radiation (direct radiative forcing) and indirectly by modifying the microphysical characteristics and lifetimes of clouds (indirect forcing). Recently, Forster et al. (2007) provided a review of several model- and observation-based estimates of clear-sky and all

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L. Liu, D. Shawki, A. Voulgarakis, M. Kasoar, B. H. Samset, G. Myhre, P. M. Forster, Ø. Hodnebrog, J. Sillmann, S. G. Aalbergsjø, O. Boucher, G. Faluvegi, T. Iversen, A. Kirkevåg, J.-F. Lamarque, D. Olivié, T. Richardson, D. Shindell, and T. Takemura

1. Introduction Understanding the influence that humans have on the planet through their emissions of anthropogenic greenhouse gases (GHGs) and aerosols is an important part of tackling the climate change challenge. The impact of these anthropogenic forcers on the hydrological cycle is one of the main topics in climate change research (e.g., Wu et al. 2013 ), since any changes to radiatively active constituents can mean changes in the patterns of rainfall, droughts, and storms, all of which

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Lixin Wu, Yan Sun, Jiaxu Zhang, Liping Zhang, and Shoshiro Minobe

) freshwater forcing over the western tropical Pacific decreases (increases) sea surface height locally and sets up a positive (negative) zonal pressure gradient anomaly, which accelerates (decelerates) the meridional overturning circulation and equatorial surface westward flow. This leads to an intensification (reduction) of meridional heat divergence and vertical cold advection, and thus a development of La Niña (El Niño)–like response in the tropics. The tropical responses are further substantiated by

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Alexandra K. Jonko, Karen M. Shell, Benjamin M. Sanderson, and Gokhan Danabasoglu

1. Introduction It has been suggested that climate sensitivity, Earth’s equilibrium surface temperature response to an external perturbation, is a constant property of the climate system that remains unchanged under different forcing magnitudes and types. Indeed, several previous model studies find little to no dependence of climate sensitivity on forcing ( Chen and Ramaswamy 1996 ; Forster et al. 2000 ; Boer and Yu 2003 ; Hansen et al. 2005 ). More recent work exploring a broader range of

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