A210-0001
MOPITT Data Enhancement Through Cloud Detection Improvement
Wednesday, 16 December 2020
Poster
Hebaalah S Marey1, James R Drummond2, Dylan B. A. Jones3, Merritt N Deeter4, Helen Marie Worden4, John C Gille5 and Sara Martinez-Alonso5, (1)University of Toronto, Toronto, ON, Canada, (2)Dalhousie University, Department of Physics and Atmospheric Science, Halifax, NS, Canada, (3)University of Toronto, Department of Physics, Toronto, ON, Canada, (4)National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling Laboratory, Boulder, CO, United States, (5)NCAR, Boulder, CO, United States
Abstract:
The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument has measured tropospheric CO continuously since March 2000, providing the longest continuous dataset of CO from space. During its long mission, data processing has been developed and updated to improve the quality of CO retrievals and the sensitivity to lower troposphere. It has a global successful retrieval rate that varies between about 30% and 40% between 90°S–90°N and 60°S–60°N, respectively. The spatial seasonal variations demonstrated that while the data coverage in some places reaches 30% in summer, this number drops to less than 10% in winter due to significant cloud cover. Therefore, different approaches were investigated to improve the current MOPITT cloud detection scheme to enhance the data coverage.
The MOPITT CO total column data were modified for some cases by suppressing the cloud detection scheme so retrievals are produced regardless the cloud status. Analysis of the CO standard (cloud filtered) and non-standard product (non-cloud masked) are conducted for some selected days. In particular, results showed a significant number of low cloud cases that were not captured in the standard product. Also, the influence of various parameters on the MOPITT radiance ratio threshold optimization was examined using numerous tools. The MOPITT radiance ratio is the ratio of MOPITT radiance relative to model calculated clear sky radiances.
The impact of changing MOPITT radiance ratio was investigated and the results indicated a significant apparent increase of MOPITT observations especially over ocean. Analysis of the cloud flag contributions for each test revealed that the gain in the number observation is a result of the increase of low cloud successful detection cases, suggesting that the current low cloud detection method is effective over ocean rather than over land. Therefore, the current cloud detection scheme needs to be refined for better low cloud detection over land.
