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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
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
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
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
1. Introduction In the late 1980s Ellingson et al. (1989) successfully developed a multispectral regression technique using the radiance observations from the High Resolution Infrared Radiation Sounder (HIRS) to estimate the outgoing longwave radiation (OLR) at the top of the atmosphere. Acknowledging its better accuracy and other advantages over the long-standing National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) OLR, which is estimated
1. Introduction In the late 1980s Ellingson et al. (1989) successfully developed a multispectral regression technique using the radiance observations from the High Resolution Infrared Radiation Sounder (HIRS) to estimate the outgoing longwave radiation (OLR) at the top of the atmosphere. Acknowledging its better accuracy and other advantages over the long-standing National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) OLR, which is estimated
shown that snow surface temperature and snow liquid water content can affect ski–snow friction ( Colbeck 1988 , 1992 ) and hence the outcome of ski races ( Fauve et al. 2005 ). The snow-surface temperature of a ski run is affected by the four components of the radiation budget: upwelling and downwelling shortwave and longwave radiation. Colbeck (1994) observed that a 4°C temperature variation is possible between shady and sunny conditions, showing the importance of downwelling shortwave radiation
shown that snow surface temperature and snow liquid water content can affect ski–snow friction ( Colbeck 1988 , 1992 ) and hence the outcome of ski races ( Fauve et al. 2005 ). The snow-surface temperature of a ski run is affected by the four components of the radiation budget: upwelling and downwelling shortwave and longwave radiation. Colbeck (1994) observed that a 4°C temperature variation is possible between shady and sunny conditions, showing the importance of downwelling shortwave radiation
important for understanding climate. Initial interest in the outgoing longwave radiation (OLR) diurnal cycle stemmed from attempts to determine the Earth energy budget from sun-synchronous satellite measurements ( Raschke and Bandeen 1970 ). Raschke and Bandeen (1970) present the first indications of OLR diurnal cycle characteristics using noon-minus-midnight differences, identifying large OLR diurnal cycles over land in desert and convective regions. Short and Wallace (1980) also used day
important for understanding climate. Initial interest in the outgoing longwave radiation (OLR) diurnal cycle stemmed from attempts to determine the Earth energy budget from sun-synchronous satellite measurements ( Raschke and Bandeen 1970 ). Raschke and Bandeen (1970) present the first indications of OLR diurnal cycle characteristics using noon-minus-midnight differences, identifying large OLR diurnal cycles over land in desert and convective regions. Short and Wallace (1980) also used day
applications in different fields and, more specifically, to accurate and fast modeling of atmospheric radiative processes ( Krasnopolsky 1997 ; Chevallier et al. 1998 ) and for satellite retrieval procedures (e.g., Krasnopolsky 1997 ; Krasnopolsky and Schiller 2003 ). The NN techniques have been successfully applied to development of a new longwave radiation parameterization (“NeuroFlux”) for the European Centre for Medium-Range Weather Forecasts (ECMWF) model ( Chevallier et al. 1998 , 2000
applications in different fields and, more specifically, to accurate and fast modeling of atmospheric radiative processes ( Krasnopolsky 1997 ; Chevallier et al. 1998 ) and for satellite retrieval procedures (e.g., Krasnopolsky 1997 ; Krasnopolsky and Schiller 2003 ). The NN techniques have been successfully applied to development of a new longwave radiation parameterization (“NeuroFlux”) for the European Centre for Medium-Range Weather Forecasts (ECMWF) model ( Chevallier et al. 1998 , 2000
1. Introduction Fluxes of radiation at the surface of the earth are intimately related to climate. The weather/climate system is a heat engine for which the source of heat is the sun’s radiation. Most of the radiation from the sun that is absorbed by the earth–atmosphere system is absorbed at the surface. When averaged over a month, the longwave radiation flux emitted by the surface and the longwave flux from the atmosphere down to the surface both exceed the radiation absorbed from the sun
1. Introduction Fluxes of radiation at the surface of the earth are intimately related to climate. The weather/climate system is a heat engine for which the source of heat is the sun’s radiation. Most of the radiation from the sun that is absorbed by the earth–atmosphere system is absorbed at the surface. When averaged over a month, the longwave radiation flux emitted by the surface and the longwave flux from the atmosphere down to the surface both exceed the radiation absorbed from the sun
1. Introduction The outgoing longwave radiation (OLR) is a critical variable as it balances the incoming solar (shortwave) radiation and shapes Earth’s climate. In essence, OLR is the irradiance flux F contributed by the outgoing radiances I emerging from the top of the atmosphere (TOA) at all possible angles. Their relationship can be expressed as Eq. (1) , assuming azimuthal homogeneity: (1) F ( υ ) = ∫ 0 2 π ∫ 0 π / 2 I ( υ , θ ) sin ( θ ) cos ( θ ) d θ d ϕ = 2 π ∫ 0 π
1. Introduction The outgoing longwave radiation (OLR) is a critical variable as it balances the incoming solar (shortwave) radiation and shapes Earth’s climate. In essence, OLR is the irradiance flux F contributed by the outgoing radiances I emerging from the top of the atmosphere (TOA) at all possible angles. Their relationship can be expressed as Eq. (1) , assuming azimuthal homogeneity: (1) F ( υ ) = ∫ 0 2 π ∫ 0 π / 2 I ( υ , θ ) sin ( θ ) cos ( θ ) d θ d ϕ = 2 π ∫ 0 π
1. Introduction Longwave radiation (LW) is a key component of the energy balance of the earth–atmosphere system and is affected by greenhouse gases and clouds, by far the most important parameters in climate change studies. Estimates of LW irradiances are generally based on parameterizations, both for cloud-free and all-sky conditions ( Allan et al. 1999 ; Ruckstuhl et al. 2007 ; Dupont et al. 2008 , among others), or radiative transfer calculations, while measurements are not as conventional
1. Introduction Longwave radiation (LW) is a key component of the energy balance of the earth–atmosphere system and is affected by greenhouse gases and clouds, by far the most important parameters in climate change studies. Estimates of LW irradiances are generally based on parameterizations, both for cloud-free and all-sky conditions ( Allan et al. 1999 ; Ruckstuhl et al. 2007 ; Dupont et al. 2008 , among others), or radiative transfer calculations, while measurements are not as conventional
climate monitoring. Because the measurement of spectrally resolved radiances can be accurately calibrated to international standards in space ( Goody and Haskins 1998 ; Anderson et al. 2004 ), and because it possesses high information content and global coverage, outgoing longwave radiation (OLR) spectrum observation makes an excellent candidate for a benchmark climate record. It has been understood that climate forcings can be detected and distinguished from their spectral signatures. Kiehl (1983
climate monitoring. Because the measurement of spectrally resolved radiances can be accurately calibrated to international standards in space ( Goody and Haskins 1998 ; Anderson et al. 2004 ), and because it possesses high information content and global coverage, outgoing longwave radiation (OLR) spectrum observation makes an excellent candidate for a benchmark climate record. It has been understood that climate forcings can be detected and distinguished from their spectral signatures. Kiehl (1983
