Atmos. Chem. Phys. Discuss., 7, 13915-13958, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Cloud type comparisons of AIRS, CloudSat, and CALIPSO cloud height and amount
B. H. Kahn1, M. T. Chahine1, G. L. Stephens2, G. G. Mace3, R. T. Marchand4, Z. Wang5, C. D. Barnet6, A. Eldering1, R. E. Holz7, R. E. Kuehn8, and D. G. Vane1
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
2Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
3Department of Meteorology, University of Utah, Salt Lake City, UT, USA
4Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA, USA
5Department of Atmospheric Science, University of Wyoming, Laramie, WY, USA
6NOAA–NESDIS, Silver Springs, MD, USA
7CIMSS–University of Wisconsin–Madison, Madison, WI, USA
8NASA Langley Research Center, Hampton, VA, USA

Abstract. The precision of the two-layer cloud height fields derived from the Atmospheric Infrared Sounder (AIRS) is explored and quantified for a five-day set of observations. Coincident profiles of vertical cloud structure by CloudSat, a 94 GHz profiling radar, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), are compared to AIRS for a wide range of cloud types. Bias and variability in cloud height differences are shown to have dependence on cloud type, height, and amount, as well as whether CloudSat or CALIPSO is used as the comparison standard. The CloudSat–AIRS biases and variability range from −4.3 to 0.5±1.2–3.6 km for all cloud types. Likewise, the CALIPSO–AIRS biases range from 0.6–3.0±1.2–3.6 km (−5.8 to −0.2±0.5–2.7 km) for clouds ≥7 km (<7 km). The upper layer of AIRS has the greatest sensitivity to Altocumulus, Altostratus, Cirrus, Cumulonimbus, and Nimbostratus, whereas the lower layer has the greatest sensitivity to Cumulus and Stratocumulus. Although the bias and variability generally decrease with increasing cloud amount, the ability of AIRS to constrain cloud occurrence, height, and amount is demonstrated across all cloud types for many geophysical conditions. In particular, skill is demonstrated for thin Cirrus, as well as some Cumulus and Stratocumulus, cloud types infrared sounders typically struggle to quantify. Furthermore, some improvements in the AIRS Version 5 operational retrieval algorithm are demonstrated. However, limitations in AIRS cloud retrievals are also revealed, including the existence of spurious Cirrus near the tropopause and low cloud layers within Cumulonimbus and Nimbostratus clouds. Likely causes of spurious clouds are identified and the potential for further improvement is discussed.

Citation: Kahn, B. H., Chahine, M. T., Stephens, G. L., Mace, G. G., Marchand, R. T., Wang, Z., Barnet, C. D., Eldering, A., Holz, R. E., Kuehn, R. E., and Vane, D. G.: Cloud type comparisons of AIRS, CloudSat, and CALIPSO cloud height and amount, Atmos. Chem. Phys. Discuss., 7, 13915-13958, doi:10.5194/acpd-7-13915-2007, 2007.
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