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Vanda Salgueiro, Maria João Costa, Ana Maria Silva, and Daniele Bortoli

and at the top of the atmosphere (TOA) ( Dong et al. 2006 ). A way of quantifying the cloud radiation effects at the surface and at the TOA is the cloud radiative forcing (CRF), which is defined as an instantaneous change in net total radiation (SW plus LW; in W m −2 ) obtained under cloudy conditions and its clear-sky counterpart; CRF can produce a cooling (negative CRF) or a warming (positive CRF) effect on the earth–atmosphere system. CRF has been a research topic over the last decades because

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Joseph Egger and Klaus-Peter Hoinka

investigation of Fig. 1 has to start from the PV equation with three-dimensional velocity v = ( u , υ , w ), where the overbar denotes the time mean state and the prime deviations from the mean. It is assumed in (1.2) that the flow is incompressible and that dissipative effects can be represented by a simple damping term. Forcing by heating is excluded. The deviations contain all available time scales. Multiplication of (1.2) by yields, after simple manipulations and after taking expectations

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Minghong Zhang and Yi Huang

1. Introduction In the analysis of climate sensitivity, it is a convention to consider radiative forcing to comprise both instantaneous forcing that is due to perturbation in radiative gases (e.g., CO 2 ) and contributions by rapid adjustments of other atmospheric components that are not related to surface temperature change ( Ramaswamy et al. 2001 ). For instance, stratospheric temperature adjustment resulting from the radiative cooling effect of CO 2 is usually considered part of the CO 2

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Arindam Samanta, Bruce T. Anderson, Sangram Ganguly, Yuri Knyazikhin, Ramakrishna R. Nemani, and Ranga B. Myneni

roughly corresponds to the base year 1990 CO 2 concentration (355 ppmv) adopted by the Kyoto Protocol and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) ( Solomon et al. 2007 ). The intervening 350-ppmv CO 2 increase corresponds to a radiative forcing of 3.6 W m −2 , which is well within the realm of what can be expected in the twenty-first century from anthropogenic contributions of radiatively active chemical constituents to the atmosphere, absent

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Bjorn Stevens

Following the notation introduced by Stevens (2015 , hereafter S15) I denote the anthropogenic aerosol forcing by and globally averaged SO 2 emissions by where t denotes time, measured in years. For the sake of argument, assume that both aerosol–cloud and aerosol–radiation interactions contribute to forcings that scale linearly with , as advocated by Kretzschmar et al. (2017) , and also Booth et al. (2018) . In this case, By requiring the forced (globally averaged) temperature

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Nicholas Lewis and Judith Curry

1. Introduction There has been considerable scientific investigation of the magnitude of the warming of Earth’s climate from changes in atmospheric carbon dioxide (CO 2 ) concentration. Two standard metrics summarize the sensitivity of global surface temperature to an externally imposed radiative forcing. Equilibrium climate sensitivity (ECS) represents the equilibrium change in surface temperature to a doubling of atmospheric CO 2 concentration. Transient climate response (TCR), a shorter

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Jeffrey M. Chagnon

of momentum flux [see review by Fritts and Alexander (2003) and references therein]. A problem that is complimentary to the wave–mean flow interaction problem is the wave–forcing interaction problem. The latter has received relatively less scrutiny in the literature (exceptions noted below) but may be of significance to mesoscale dynamics in the troposphere. The wave–forcing interaction problem is of particular relevance to convectively generated waves that, unlike topographically forced waves

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K. E. Taylor, M. Crucifix, P. Braconnot, C. D. Hewitt, C. Doutriaux, A. J. Broccoli, J. F. B. Mitchell, and M. J. Webb

temperature change. The radiative “forcing” of the system is commonly quantified in terms of the immediate impact of any imposed change on the TOA fluxes. 1 An imposed increase in CO 2 concentration, for example, promptly reduces, by a small amount, the longwave radiation emanating to space and is therefore considered a radiative forcing. The radiative imbalance caused by this forcing tends to warm the system and, in any given model, the global mean temperature response is roughly proportional to the

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K. M. Markowicz, P. J. Flatau, J. Remiszewska, M. Witek, E. A. Reid, J. S. Reid, A. Bucholtz, and B. Holben

and middle-troposphere subsidence are responsible for the mostly clear-sky conditions; thus, it was a good site to study the direct aerosol radiative forcing. The purpose of this study is to extend previous knowledge about the aerosol optical properties in the Middle East region. We investigate the influence of aerosol on the surface radiation budget. The results are based on the data collected during 6 weeks of measurements performed at the MAARCO site, including surface and columnar observations

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Stefano Materia, Paul A. Dirmeyer, Zhichang Guo, Andrea Alessandri, and Antonio Navarra

participating in the Second Global Soil Wetness Project (GSWP-2; Dirmeyer et al. 2006 ; see Table 1 ) are used as forcings for the Hydrology Discharge (HD) model ( Hagemann and Dümenil 1998a ). The response of river discharges produced by HD to the different surface and subsurface runoff values is evaluated. Moreover, the quality of meteorological forcing data has a strong influence on the simulation of land surface components of the hydrological cycle ( Guo et al. 2006 ). GSWP-2 included a number of

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