Long-term global distribution of earth's shortwave radiation budget at the top of atmosphere

Abstract

Abstract. The mean monthly shortwave (SW) radiation budget at the top of atmosphere (TOA) was computed on 2.5 • longitude-latitude resolution for the 14-year period from 1984 to 1997, using a radiative transfer model with long-term climatological data from the International Satellite Cloud Climatology Project (ISCCP-D2) supplemented by data from the National Centers for Environmental Prediction -National Center for Atmospheric Research (NCEP-NCAR) Global Reanalysis project, and other global data bases such as TIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set (GADS). The model radiative fluxes at TOA were validated against Earth Radiation Budget Experiment (ERBE) S4 scanner satellite data (1985)(1986)(1987)(1988)(1989). The model is able to predict the seasonal and geographical variation of SW TOA fluxes. On a mean annual and global basis, the model is in very good agreement with ERBE, overestimating the outgoing SW radiation at TOA (OSR) by 0.93 Wm −2 (or by 0.92%), within the ERBE uncertainties. At pixel level, the OSR differences between model and ERBE are mostly within ±10 Wm −2 , with ±5 Wm −2 over extended regions, while there exist some geographic areas with differences of up to 40 Wm −2 , associated with uncertainties in cloud properties and surface albedo. The 14-year average model results give a planetary albedo equal to 29.6% and a TOA OSR flux of 101.2 Wm −2 . A significant linearly decreasing trend in OSR and planetary albedo was found, equal to 2.3 Wm −2 and 0.6% (in absolute values), respectively, over the 14-year period (from January 1984 to December 1997)

Aerosol shortwave direct radiative effect and forcing based on MODIS Level 2 data in the Eastern Mediterranean (Crete)

“…Previous, spectral or simpler (broadband) versions of the model have been used by Vardavas and Koutoulaki (1995), Vardavas (1999, 2001) and Hatzianastassiou et al (2004aHatzianastassiou et al ( , b, 2005Hatzianastassiou et al ( , 2007, to compute the shortwave (SW) radiation budget and the aerosol direct radiative effect on global scales (see also Vardavas and Taylor, 2011).…”

“…Reflection of incident solar radiation from the Earth's surface is taken into account and the surface reflectivity, R g , is treated as explained by Hatzianastassiou et al (2004a). In our case, the radiative computations are performed over two coastal areas.…”

“…The incoming solar irradiance at the top of the atmosphere is computed based on the spectral profile of Gueymard (2004), using a solar constant S 0 = 1367 Wm −2 (Hartmann, 1994;Willson, 1997) corrected for the Earth's elliptical orbit, as explained by Hatzianastassiou et al (2004a). The computations are performed separately for 118 wavelengths in the range 0.2-1.0 µm, and 10 spectral bands in the range 1.0-10 µm.…”

“…For the computation of the cloud shortwave transmissivity and reflectivity in the near-IR, a radiation transfer model also requires cloud absorption as well as scattering optical depth. These were derived from the τ s c values given by MODIS, based on Mie computations as described in Hatzianastassiou et al (2004a) for both liquid and ice clouds. For the UVvisible range, g c is set equal to 0.85 and 0.78 for liquid and ice clouds respectively, while for the near-IR the corresponding values are 0.82 and 0.80 (Hatzianastassiou et al, 2004a).…”

Evaluation of the radiation budget with a regional climate model over Europe and inspection of dimming and brightening

“…Knowledge of the Earth's energy balance between the energy absorbed and the amount escaping from the Earth is critical in determining the overall climate and its changes [e.g., Hansen et al, 2005]. Great effort has been made to measure top of atmosphere (TOA) radiative components both in the longwave (LW) and shortwave (SW) part of the spectrum with satellite sensors and recently with greater accuracy [Loeb et al, 2009] as well as with satellite-derived estimations [Hatzianastassiou et al, 2004]. These satellite missions (e.g., Earth Radiation Budget Experiment and Clouds and the Earth's Radiant Energy System (CERES)) have provided validation data to fully assess and improve the representation of TOA radiative fluxes in general circulation models (GCMs) for present-day analysis [Chevallier and Morcrette, 2000;Wild and Roeckner, 2006;Ringer and Allan, 2004;Bodas-Salcedo et al, 2008] and with reference to a future study of their changes [Trenberth and Fasullo, 2009] as well as providing data needed to diagnose the net radiation imbalance of the Earth [Loeb et al, 2012].…”