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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D09110, doi:10.1029/2007JD009219, 2008

Spectrally resolved fluxes derived from collocated AIRS and CERES measurements and their application in model evaluation: Clear sky over the tropical oceans

Xianglei Huang

Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA


Wenze Yang

Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA


Norman G. Loeb

Radiation and Climate Branch, NASA Langley Research Center, Hampton, Virginia, USA


V. Ramaswamy

Geophysical Fluid Dynamics Laboratory, NOAA, Princeton University, Princeton, New Jersey, USA


Abstract

Spectrally resolved outgoing thermal-IR flux, the integrand of the outgoing longwave radiation (OLR), has a unique value in evaluating model simulations. Here we describe an algorithm for deriving such clear-sky outgoing spectral flux through the entire thermal-IR spectrum from the collocated Atmospheric Infrared Sounder (AIRS) and the Clouds and the Earth's Radiant Energy System (CERES) measurements over the tropical oceans. On the basis of the predefined scene types in the CERES Single Satellite Footprint (SSF) data set, spectrally dependent ADMs are developed and used to estimate the spectral flux each AIRS channel. A multivariate linear prediction scheme is then used to estimate spectral fluxes at frequencies not covered by the AIRS instrument. The whole algorithm is validated using synthetic spectra as well as the CERES OLR measurements. Using the GFDL AM2 model simulation as a case study, applications of the derived clear-sky outgoing spectral fluxes in model evaluation are illustrated. By comparing the observed spectral fluxes and simulated ones for the year of 2004, compensating errors in the simulated OLR from different absorption bands are revealed, along with the errors from frequencies within a given absorption band. Discrepancies between the simulated and observed spatial distributions and seasonal evolutions of the spectral fluxes are further discussed. The methodology described in this study can be applied to other surface types as well as cloudy-sky observations and also to corresponding model evaluations.

Received 25 July 2007; accepted 30 January 2008; published 10 May 2008.

Keywords: clear-sky spectral flux; model evaluation.

Index Terms: 3360 Atmospheric Processes: Remote sensing; 1626 Global Change: Global climate models (3337, 4928); 3359 Atmospheric Processes: Radiative processes; 3310 Atmospheric Processes: Clouds and cloud feedbacks.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 878998 bytes)

Citation: Huang, X., W. Yang, N. G. Loeb, and V. Ramaswamy (2008), Spectrally resolved fluxes derived from collocated AIRS and CERES measurements and their application in model evaluation: Clear sky over the tropical oceans, J. Geophys. Res., 113, D09110, doi:10.1029/2007JD009219.