Toward Consistent Long-term Records of Cloud Fraction from MODIS and VIIRS for CERES
Abstract
In order to produce a long-term and stable climate record of Earth's energy budget for NASA's Clouds and Earth's Radiant Energy System (CERES) project, a consistent cloud fraction record across different measurement platforms is a crucial first step. The CERES Edition (Ed) 4 cloud mask based on Terra and Aqua MODIS data has been used to generate cloud fractions for CERES Ed4 Top of Atmosphere (TOA) fluxes. As the Terra and Aqua satellites are now approaching the end of their operational lifetime, VIIRS observations on Suomi NPP and on JPSS1/JPSS2 will be used for cloud detection to continue the long-term Earth energy budget record. Since the VIIRS and MODIS instruments have different characteristics, including different spatial resolutions that depend on scan angle, and different spectral channels, our ability to derive consistent cloud properties from these two sensors with no artificial discontinuities in the time series is complicated and still uncertain.
This paper will present progress toward developing consistent cloud detection methods for application to MODIS and VIIRS. Several approaches will be evaluated. In the first approach, the MODIS and VIIRS algorithms are not unified in that they incorporate different channel complements. In the second approach, a revised cloud mask is developed for MODIS that utilizes only the channels that are also available on VIIRS. In this version, previous dependencies on the water vapor channel at 6.7 micron and a CO2 channel at 13.3 micron are removed since these channels are absent on VIIRS. The removal of these two channels is expected to be most significant in polar regions, thus there is potential to reduce accuracy in some areas at the expense of continuity. Some further tuning to the algorithms is also applied to help reduce these effects. Results and comparisons of the various methods will be presented along with comparisons to CALIPSO, which serves as a useful baseline. It is expected that this work will contribute to an improved cloud climate data record with the goal of minimizing artificial discontinuities in the time series as the record transitions from MODIS to VIIRS.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A43K3067T
- Keywords:
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- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0321 Cloud/radiation interaction;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 1640 Remote sensing;
- GLOBAL CHANGE