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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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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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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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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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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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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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Maria A. A. Rugenstein, Jonathan M. Gregory, Nathalie Schaller, Jan Sedláček, and Reto Knutti

1. Introduction and tropospheric adjustment The response of the global energy budget to an external perturbation of the energy content can be described by the heat uptake of ocean, ice, and land ( N ), the perturbation or radiative forcing ( F ), and the feedback response ( λT ), with the climate feedback parameter λ and temperature anomaly T : with the heat capacity of the climate system, C . Changes that are mediated by the climate system’s response to the perturbation are called feedback

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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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Meelis J. Zidikheri and Jorgen S. Frederiksen

1. Introduction The attribution of climate change to a particular forcing agent (e.g., greenhouse gases, aerosols, volcanic activity, land use) is a problem of great significance in climate science. The most established systematic methodology of climate change detection and attribution is the “fingerprint” method ( Hasselmann 1993 ; Hegerl et al. 1996 ; Hasselmann 1997 ), which is a statistical method of relating the observed climate response to model responses. In this approach, one needs

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Adam R. Edson and Peter R. Bannon

1. Introduction Rossby’s (1938) introduction of the adjustment problem used a momentum forcing to represent a sudden deposition of horizontal momentum into an infinite strip of the ocean by a surface wind stress. The Coriolis force associated with this flow would initially not be in balance with the pressure field and an adjustment would ensue. The original reduced-gravity shallow-water problem has been thoroughly examined [ Cahn (1945) ; Mihaljan (1963) ; see Blumen (1972) for a review

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