Global atmospheric downward longwave radiation at the surface from ground-based observations, satellite retrievals, and reanalyses

摘要: [1] Atmospheric downward longwave radiation at the surface (Ld) varies with increasing CO2 and other greenhouse gases. This study quantifies uncertainties of current estimates global Ld monthly to decadal timescales its climatology trends during past decades by a synthesis existing observations, reanalyses, satellite products. We find that observations have standard deviation error ~3.5 W m−2 on scale. Observations different pyrgeometers may differ substantially for lack reference. The calibration pyrgeometer significantly affects quantification annual variability. Compared collected 169 land sites from 1992 2010, derived state-of-the-art cloud reanalysis temperature humidity profiles grid scale ~1° has bias ±9 7 m−2, nearly zero overall bias. deviations are reduced 4 over tropical oceans when compared 24 buoy 2002 2011. −4 retrievals is likely because overestimation resulting solar heating pyrgeometer. Our best estimate means 2003 2010 342 ± 3 (global), 307 ± 3 (land), 356 ± 3 (ocean). Estimates seriously compromised changes in sensors giving water vapor profiles.