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A strict test in climate modeling with spectrally resolved radiances: GCM simulation versus AIRS observations
Author(s) -
Huang Yi,
Ramaswamy V.,
Huang Xianglei,
Fu Qiang,
Bardeen Charles
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl031409
Subject(s) - radiance , environmental science , water vapor , longwave , atmospheric infrared sounder , outgoing longwave radiation , diurnal cycle , climate model , atmospheric sciences , climatology , gcm transcription factors , meteorology , radiative transfer , remote sensing , general circulation model , climate change , physics , geology , optics , oceanography , convection
The spectrally resolved infrared radiances observed by AIRS provide a strict and insightful test for general circulation models (GCMs). We compare the clear‐ and total‐ sky spectra simulated from the Geophysical Fluid Dynamics Laboratory GCM using a high resolution radiation code with the AIRS observations. After ensuring consistency in the sampling of the observed and simulated spectra and a proper representation of clouds in the radiance simulation, the observed and simulated global‐mean radiances are shown to agree to within 2 K in the window region. Radiance discrepancies in the water vapor v 2 (1300–1650 cm −1 ) and carbon dioxide v 2 (650–720 cm −1 ) bands are consistent with the model biases in atmospheric temperature and water vapor. The existence of radiance biases of opposite signs in different spectral regions suggests that a seemingly good agreement of the model's broadband longwave flux with observations may be due to a fortuitous cancellation of spectral errors. Moreover, an examination of the diurnal difference spectrum indicates pronounced biases in the model‐simulated diurnal hydrologic cycle over the tropical oceans, a feature seen to occur in other GCMs as well.