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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 3 | Copyright
Atmos. Meas. Tech., 11, 1515-1528, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Mar 2018

Research article | 16 Mar 2018

Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties

Mark Richardson1 and Graeme L. Stephens1,2 Mark Richardson and Graeme L. Stephens
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
  • 2Department of Meteorology, University of Reading, Reading, RG6 6BB, UK

Abstract. Information content analysis is used to select channels for a marine liquid cloud retrieval using the high-spectral-resolution oxygen A-band instrument on NASA's Orbiting Carbon Observatory-2 (OCO-2). Desired retrieval properties are cloud optical depth, cloud-top pressure and cloud pressure thickness, which is the geometric thickness expressed in hectopascals. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5–764.6nm and perform a series of synthetic retrievals with perturbed initial conditions. We estimate posterior errors from the sample standard deviations and obtain ±0.75 in optical depth and ±12.9hPa in both cloud-top pressure and cloud pressure thickness, although removing the 10% of samples with the highest χ2 reduces posterior error in cloud-top pressure to ±2.9hPa and cloud pressure thickness to ±2.5hPa. The application of this retrieval to real OCO-2 measurements is briefly discussed, along with limitations and the greatest caution is urged regarding the assumption of a single homogeneous cloud layer, which is often, but not always, a reasonable approximation for marine boundary layer clouds.

Publications Copernicus
Short summary
This study analyses how much information can be obtained about liquid clouds over oceans using measurements of reflected sunlight by the OCO-2 satellite. We find that using 75 of the 853 functioning oxygen A-band channels is sufficient to retrieve cloud optical depth, and the height and thickness of the cloud in terms of atmospheric pressure coordinates, to better than 3 hPa.
This study analyses how much information can be obtained about liquid clouds over oceans using...