Tropospheric Carbon Monoxide Variability from AIRS and IASI Under Cloudy Conditions
Abstract
Satellite measurements using the thermal spectral regions are affected by the presence of clouds, and therefore, it is necessary to remove the effects of clouds before retrieving many geophysical properties. AIRS Level 2 retrieval algorithm utilizes cloud clearing to handle cloud contaminations in the signals and this increases the data coverage significantly to a yield of 50-70% of the total measurements. For the size of AIRS footprints of approximately 13.5km2 at nadir, the number of pure clear pixels is only 5-10%, which would not have been sufficient to provide daily products for monitoring purposed. The IASI retrievals from NOAA use a similar technique for cloud clearing as in AIRS such that we need to first understand the effects of the AIRS cloud-clearing on the overall quality of the retrievals. We select AIRS clear pixels using collocated MODIS cloud mask with the ratio of MODIS clear pixels in each AIRS pixel to be greater than 99%. We then analyze the CO distribution and variability in parallel with clear verses cloud-cleared pixels to study the statistical property of the two ensamples. To understand the tropospheric CO distributions and variability using cloud-cleared radiances, we examine the CO VMRs using PDFs for the entire AIRS and IASI data records. We also introduce a method to separate the background CO VMRs from the fresh emissions so that the trend of the data records can be analyzed separately.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A33I0275W
- Keywords:
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- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud/radiation interaction;
- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry