Insights into 3D cloud radiative transfer for OCO-2
Abstract
Clouds impose radiance perturbations upon Orbiting Carbon Observatory (OCO-2) measured spectra. The Spherical Harmonic Discrete Ordinate radiative transfer Method (SHDOM) code is applied in idealized bar cloud calculations of 1D and 3D radiances in order to understand 3D cloud effects for a wide range of gas vertical optical depths, solar and sensor viewing geometries. SHDOM calculations for 36 ocean and land scenes are co-analyzed with Moderate Resolution Imaging Spectroradiometer (MODIS) radiance-based nearest cloud distance data, and OCO-2 Lite file rawXCO2 values for both Quality Flag=0, (QF0, best quality) and Quality Flag=1 (QF1, poor quality) data. Analyses of several scenes indicate that OCO-2 retrievals are located between clouds and that there are few retrievals associated with cloud shadowing effects. Differences (dP) in retrieved and reanalysis meteorological surface pressure take on increasingly negative values, as nearest cloud distance approaches zero, especially for the ocean glint QF1 data, which provide the clearest evidence of 3D cloud effects in OCO-2 retrievals. Average differences in rawXCO2 at cloud distances near 20 and 0 km are an appropriate measure of 3D cloud effect biases, and are calculated for 10° latitude bands for 2015-2018. The ocean glint QF0 (QF1) averages of the 10° latitude band 3D rawXCO2 biases are near 0.4 (1.5) ppm.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.A14E..01M