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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/amt-2017-314
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties
Mark Richardson1 and Graeme L. Stephens1,2 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
2Department of Meteorology, University of Reading, Reading, RG6 6BB, UK
Abstract. An 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 pressure thickness and cloud-top pressure and the optimal channels depend on the atmospheric state, cloud properties and position within the OCO-2 swath. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5–764.6 nm 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, ±12.9 hPa 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 ±2.9 hPa and cloud pressure thickness to ±2.5 hPa. 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.

Citation: Richardson, M. and Stephens, G. L.: Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-314, in review, 2017.
Mark Richardson and Graeme L. Stephens
Mark Richardson and Graeme L. Stephens
Mark Richardson and Graeme L. Stephens

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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 1,016 oxygen A-band channels are sufficient to retrieve cloud optical depth, and the height and thickness of the cloud in terms of atmospheric pressure coordinates, to better than 3 hectoPascales.
This study analyses how much information can be obtained about liquid clouds over oceans using...
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