Analysis of 3D Cloud Effects in OCO-2 XCO2 Retrievals
Abstract
We calculate empirically the size of 3D Cloud Effects (in ppmv) that impact OCO-2 XCO2 retrievals. We analyze OCO-2 Lite file XCO2 in conjunction with MODIS Cloud Mask fields, and calculate 3D cloud effect metrics (e.g. distance from an observation point to the nearest cloud). The analysis is done for each season in 20° latitude bands for "Raw XCO2" (XCO2 retrieved before the "Bias correction" process is done) and for OCO-2 Lite file "Bias corrected XCO2". Graphs of y = XCO2 vs x= nearest cloud distance reveals the size of the 3D cloud effects. The effects are non-linear, and increase in size as the nearest cloud distance decreases. The effects are largest for OCO-2 Quality Flag (QF=1, lesser quality) data, and smaller for Quality Flag (QF=0, best) data. A sensitivity calculation is carried out to assess the approximate quantitative impact of 3D cloud effects on retrieved XCO2. The 3D cloud effects are on the order of 0.3 and 1 to 2 ppmv for QF=0 and QF=1 data, respectively. Since the Bias Correction process imparts a correction to the raw retrieved XCO2 on the order of 2 ppmv, the 3D cloud effects are fairly small for the QF=0 data, but substantial for the QF=1 data.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A41S2629M
- Keywords:
-
- 0315 Biosphere/atmosphere interactions;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES