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Atmospheric Radiation Working Group (ARWG)

This document is a summary of the major problems in atmospheric radiation, together with recommendations for appropriate action, as evaluated by the U.S. Atmospheric Radiation Working Group (ARWG). It is intended for information and possible use by atmospheric scientists, scientific committees, agencies engaged in the support of atmospheric research, and those who have the responsibility for planning future scientific programs.

The report summarizes the present status and outlines the major unsolved problems of the following five aspects of atmospheric radiation: 1) radiative transfer in realistic atmospheres, 2) radiative energy budgets, 3) radiative properties of atmosphere and surface, 4) radiative instruments and measurements, and 5) radiative interactions in dynamical systems. The final, and probably most important, section consists of recommendations for action that can be taken now to start filling the gaps in our knowledge of atmospheric radiation which are considered by the ARWG to be of highest priority. A list of members of the ARWG steering committee is included in the Appendix.

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Hiroyuki Kurokawa and Taishi Nakamoto

1. Introduction The limit of the planetary radiation (the so-called longwave radiation) of an ocean planet is determined by various mechanisms called “radiation limits.” These radiation limits are important when considering the formation of an ocean ( Abe and Matsui 1988 ) and when attempting to determining the habitable zone of exoplanets ( Kasting et al. 1993 ). The radiation limits are related to the inner edge of the habitable zone. The radiation limits (or runaway greenhouse effect) were

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Rosie Howard and Roland Stull

1. Introduction The surface radiation budget in snow-covered mountainous terrain is important in hydrology ( Fierz et al. 2003 ), snowmelt modeling ( Plüss and Ohmura 1997 ; Sicart et al. 2006 ), and glacier energy balance investigations ( Brock et al. 2010 ). Avalanche forecasting and safety studies ( McClung 2002a , b ; McClung and Schaerer 2006 ) show the significance of the radiation budget for a natural alpine snowpack. Ski racing takes place on manually prepared ski pistes. It has been

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S. M. S. Costa and K. P. Shine

article is intended to be a pedagogical discussion of one component of the KT97 figure [which was not updated in Trenberth et al. (2009) ], which is the amount of longwave radiation labeled “atmospheric window.” KT97 estimate this component to be 40 W m −2 compared to the total outgoing longwave radiation (OLR) of 235 W m −2 ; however, KT97 make clear that their estimate is “somewhat ad hoc” rather than the product of detailed calculations. The estimate was based on their calculation of the

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Kaicun Wang and Shunlin Liang

1. Introduction Surface net radiation R n is the sum of incident downward and upward shortwave and longwave radiation: where S ↓ and S ↑ are the surface downward and upward shortwave radiation, L ↓ and L ↑ are the surface downward and upward longwave radiation, α is surface albedo, and S n is surface net shortwave radiation. The downward components of R n are controlled by solar zenith angle (i.e., time of day, season, and latitude), cloud amount, atmospheric water vapor amount

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Vincent E. Larson, Kurt E. Kotenberg, and Norman B. Wood

participants can easily implement the same radiative formula. Second, LESs usually last 6 h or less, a period too short to heat or cool clear air significantly, thereby vitiating the advantage of accurate multiband radiative calculations for gaseous absorption. Third, an analytic longwave formula is computationally inexpensive. This is advantageous because considerable expense is associated with both LES and numerical radiation calculations. LES is expensive because it requires a small grid size (often

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Evelyn Jäkel, Manfred Wendisch, Mario Blumthaler, Rainer Schmitt, and Ann R. Webb

1. Introduction Accurate atmospheric measurements of spectral ultraviolet (UV) radiation (290–400 nm) are challenging, in particular, in spatially inhomogeneous atmospheric and surface albedo conditions. The absorption of UV radiation due to the stratospheric ozone causes a strong decrease of the downward UV reaching the troposphere. It causes a sudden drop of the spectral radiation of several orders of magnitudes toward smaller wavelengths ( λ ), which is referred to as the atmospheric cutoff

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Bolei Yang and Zhe-Min Tan

.g., Nicholls and Montgomery 2013 ; Nicholls 2015 ). Three leading mechanisms have been postulated to explain how radiation can affect convective activity ( Fig. 1 ). First, the stratification could be changed by large-scale nocturnal environmental cooling (e.g., Dudhia 1989 ; Tao et al. 1996 ; Melhauser and Zhang 2014 ; Tang and Zhang 2016 ). The absence of shortwave heating makes the troposphere cooler at night, which favors convection by increasing relative humidity and enhancing convective

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M. Q. Brewster, X. Li, K. K. Roman, E. O. McNichols, and M. J. Rood

1. Introduction, background, motivation, and objectives The potential importance of the effect of thermal radiation on cloud droplet evolution and behavior has been known for well over a century. In 1877 Osborne Reynolds pointed out that, at cloud top, longwave (LW) thermal radiation between cloud droplets and a much colder, remote radiative heat sink such as outer space could induce a temperature difference between droplets and surrounding air that was of same order as that induced by

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Vladimir M. Krasnopolsky, Michael S. Fox-Rabinovitz, and Alexei A. Belochitski

1. Introduction One of the main problems in development and implementation of state-of-the-art numerical climate and weather prediction models is the complexity of physical processes involved. Some of the model physics parameterizations, such as radiation, are time consuming even for most powerful modern supercomputers, and because of that are calculated less frequently than other model physics components and model dynamics. This may negatively affect the accuracy of a model’s physics

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