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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D09S14, doi:10.1029/2005JD006103, 2006

Atmospheric Radiation Measurement site atmospheric state best estimates for Atmospheric Infrared Sounder temperature and water vapor retrieval validation

David C. Tobin

Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA


Henry E. Revercomb

Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA


Robert O. Knuteson

Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA


Barry M. Lesht

Argonne National Laboratory, Argonne, Illinois, USA


L. Larrabee Strow

Department of Physics, University of Maryland Baltimore County, Baltimore, Maryland, USA


Scott E. Hannon

Department of Physics, University of Maryland Baltimore County, Baltimore, Maryland, USA


Wayne F. Feltz

Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA


Leslie A. Moy

Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA


Eric J. Fetzer

NASA Jet Propulsion Laboratory, Pasadena, California, USA


Ted S. Cress

Pacific Northwest National Laboratory, Richland, Washington, USA


Abstract

The Atmospheric Infrared Sounder (AIRS) is the first of a new generation of advanced satellite-based atmospheric sounders with the capability of obtaining high–vertical resolution profiles of temperature and water vapor. The high-accuracy retrieval goals of AIRS (e.g., 1 K RMS in 1 km layers below 100 mbar for air temperature, 10% RMS in 2 km layers below 100 mbar for water vapor concentration), combined with the large temporal and spatial variability of the atmosphere and difficulties in making accurate measurements of the atmospheric state, necessitate careful and detailed validation using well-characterized ground-based sites. As part of ongoing AIRS Science Team efforts and a collaborative effort between the NASA Earth Observing System (EOS) project and the Department of Energy Atmospheric Radiation Measurement (ARM) program, data from various ARM and other observations are used to create best estimates of the atmospheric state at the Aqua overpass times. The resulting validation data set is an ensemble of temperature and water vapor profiles created from radiosondes launched at the approximate Aqua overpass times, interpolated to the exact overpass time using time continuous ground-based profiles, adjusted to account for spatial gradients within the Advanced Microwave Sounding Unit (AMSU) footprints, and supplemented with limited cloud observations. Estimates of the spectral surface infrared emissivity and local skin temperatures are also constructed. Relying on the developed ARM infrastructure and previous and ongoing characterization studies of the ARM measurements, the data set provides a good combination of statistics and accuracy which is essential for assessment of the advanced sounder products. Combined with the collocated AIRS observations, the products are being used to study observed minus calculated AIRS spectra, aimed at evaluation of the AIRS forward radiative transfer model, AIRS observed radiances, and temperature and water vapor profile retrievals. This paper provides an introduction to the ARM site best estimate validation products and characterizes the accuracy of the AIRS team version 4 atmospheric temperature and water vapor retrievals using the ARM products. The AIRS retrievals over tropical ocean are found to have very good accuracy for both temperature and water vapor, with RMS errors approaching the theoretical expectation for clear sky conditions, while retrievals over a midlatitude land site have poorer performance. The results demonstrate the importance of using specialized “truth” sites for accurate assessment of the advanced sounder performance and motivate the continued refinement of the AIRS science team retrieval algorithm, particularly for retrievals over land.

Received 20 April 2005; accepted 19 July 2005; published 16 March 2006.

Keywords: satellite; sounding; validation.

Index Terms: 0394 Atmospheric Composition and Structure: Instruments and techniques; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 1640 Global Change: Remote sensing (1855).

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Citation: Tobin, D. C., H. E. Revercomb, R. O. Knuteson, B. M. Lesht, L. L. Strow, S. E. Hannon, W. F. Feltz, L. A. Moy, E. J. Fetzer, and T. S. Cress (2006), Atmospheric Radiation Measurement site atmospheric state best estimates for Atmospheric Infrared Sounder temperature and water vapor retrieval validation, J. Geophys. Res., 111, D09S14, doi:10.1029/2005JD006103.