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

[摘要] The mean monthly shortwave (SW) radiation budget at the top of atmosphere(TOA) was computed on 2.5° longitude-latitude resolution for the 14-yearperiod from 1984 to 1997, using a radiative transfer model with long-termclimatological data from the International Satellite Cloud ClimatologyProject (ISCCP-D2) supplemented by data from the National Centers forEnvironmental Prediction – National Center for Atmospheric Research(NCEP-NCAR) Global Reanalysis project, and other global data bases such asTIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set(GADS). The model radiative fluxes at TOA were validated against EarthRadiation Budget Experiment (ERBE) S4 scanner satellite data (1985–1989).The model is able to predict the seasonal and geographical variation of SWTOA fluxes. On a mean annual and global basis, the model is in very goodagreement with ERBE, overestimating the outgoing SW radiation at TOA (OSR)by 0.93 Wm^-2 (or by 0.92%), within the ERBE uncertainties. At pixellevel, the OSR differences between model and ERBE are mostly within ±10 Wm^-2,with ±5 Wm^-2 over extended regions, while there existsome geographic areas with differences of up to 40 Wm^-2, associatedwith uncertainties in cloud properties and surface albedo. The 14-yearaverage model results give a planetary albedo equal to 29.6% and a TOAOSR flux of 101.2 Wm^-2. A significant linearly decreasing trend in OSRand planetary albedo was found, equal to 2.3 Wm^-2 and 0.6% (in absolute values), respectively, over the14-year period (from January 1984 to December 1997), indicating anincreasing solar planetary warming. This planetary SW radiative heatingoccurs in the tropical and sub-tropical areas (20° S–20° N), withclouds being the most likely cause. The computed global mean OSR anomalyranges within ±4 Wm^-2, with signals from El Niño and La Niñaevents or Pinatubo eruption, whereas significant negative OSR anomalies,starting from year 1992, are also detected.

[学科分类] 大气科学