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Reinout Boers, Fred Bosveld, Henk Klein Baltink, Wouter Knap, Erik van Meijgaard, and Wiel Wauben

Experiment (ERBE) and the Clouds and the Earth’s Radiant Energy System (CERES). Both datasets provide top-of-atmosphere (TOA) radiative fluxes that can be used to evaluate the model cloud representation or to determine the impact of clouds on the radiation balance of Earth. An often used method to determine cloud impact is to measure cloud forcing, which is defined as the difference between the net all-sky and the net clear-sky radiant fluxes ( Charlock and Ramanathan 1985 ). However, TOA fluxes only

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Virendra P. Ghate, Bruce A. Albrecht, Christopher W. Fairall, and Robert A. Weller

lack of direct observations for the verification and evaluation of model representations of this region. In this study we present climatology of the SEP region using data from the Stratus ORS, collected during January 2001 to December 2005. The annual cycle of the surface meteorological parameters and surface fluxes is presented in section 2 . Cloud fraction is determined using a simple model in section 3 . Annual and diurnal changes in the cloud radiative forcing are discussed in section 4

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James R. Campbell, Simone Lolli, Jasper R. Lewis, Yu Gu, and Ellsworth J. Welton

1. Background Cirrus clouds have long been recognized for their unique contribution to climate ( Liou 1986 ). In particular, whereas all clouds warm the underlying atmosphere and surface at night [positive top-of-the-atmosphere (TOA) forcing], cirrus is the only genus that can readily warm or cool (negative TOA forcing; effectively all other clouds cool the daytime atmosphere) the daytime atmosphere and surface depending on the cirrus’s varying physical characteristics [i.e., cloud height

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Gerald G. Mace and Sally Benson

-term data also makes the statistics relevant for evaluation of similar quantities derived from general circulation models because the statistics would be representative of regional conditions and not just the specific point at which the data were collected. This long time series also allows us to better quantify the uncertainty of the derived cloud radiative forcing by comparing fluxes at the surface and TOA. 2. Methodology and validation The primary purpose of the ACRF is to provide continuous

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Yulan Hong and Guosheng Liu

albedo effect ( Liou 1986 ). As optical depth increases, solar albedo effect would dominate and therefore the magnitude and sign of the ice cloud radiative forcing would rely largely on its optical thickness. Where this warming–cooling separation occurs in natural ice clouds is an interesting scientific question. Classifications have been made for ice clouds to better study their properties. For instance, Sassen and Cho (1992) defined three categories of cirrus based on visible optical depth in

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Wojciech W. Grabowski

others. However, in nature, convective clouds continuously interact with their surroundings through gravity waves and detrainment that modify their environment (e.g., Bretherton and Smolarkiewicz 1989 ). These interactions affect development of subsequent clouds. Thus, it is irrelevant what the first cloud does, but what matters is a response of an ensemble of clouds to realistic forcings averaged over many cloud realizations. (An exception to this argument might be when the first cloud causes a

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Timothy W. Cronin

of 0.5 has been widely used. The early studies of radiative–convective equilibrium by Manabe and Strickler (1964) , Manabe and Wetherald (1967) , Ramanathan (1976) , and the early review paper by Ramanathan and Coakley (1978) all took . The daytime-average zenith angle has also been used in simulation of climate on other planets (e.g., Wordsworth et al. 2010 ) as well as estimation of global radiative forcing by clouds and aerosols ( Fu and Liou 1993 ; Zhang et al. 2013 ). To our

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Jeongbin Seo, Sarah M. Kang, and Dargan M. W. Frierson

function of temperature. Hence, there are no water vapor– and cloud–radiative feedbacks. It has T42 horizontal resolution with 25 vertical levels. Both models are coupled to an aquaplanet slab mixed layer ocean of 2.4-m depth. The shallow mixed layer is used to shorten the time to reach equilibrium. The models are run for 8 years with the results shown averaged over the last 6 years. The experiments are designed to examine the efficiency of surface thermal forcing on shifting the ITCZ depending on its

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Guoxing Chen, Wei-Chyung Wang, and Jen-Ping Chen

consistent with the biases found in the smaller simulated shortwave cloud radiative forcing in these regions ( Calisto et al. 2014 ; Flato et al. 2014 ). It is also known that these regions have been affected by aerosols emitted from the continents. For instance, the southeast Pacific (SEP), where the largest and most persistent stratocumulus deck in the world resides, is exposed to anthropogenic aerosols produced by copper smelters in South America ( Huneeus et al. 2006 ). The increased aerosols not

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A. Gettelman, J. E. Kay, and K. M. Shell

at cooler temperatures, causing warming. Low clouds cool and high clouds warm, with the balance of effects being a net cooling ( Stephens 2005 ). Changes to cloud amount, location, and radiative properties (e.g., optical depth) can exert feedbacks on the system. Any of these feedbacks may significantly alter the magnitude of the response to radiative forcing. The water vapor feedback, for example, is large and positive ( Held and Soden 2000 ). While it is straightforward to calculate the direct

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