VIIRS Edition 1 Cloud Properties for CERES, Part 1: Algorithm Adjustments and Results

• Published in: Remote sensing (Basel, Switzerland) Vol. 15; no. 3; p. 578
• Main Authors: Minnis, Patrick, Sun-Mack, Sunny, Smith, William L., Trepte, Qing Z., Hong, Gang, Chen, Yan, Yost, Christopher R., Chang, Fu-Lung, Smith, Rita A., Heck, Patrick W., Yang, Ping
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2023
• Subjects: Algorithms; Broadband; Calibration; Cirrus clouds; cloud; cloud amount; cloud height; cloud optical depth; cloud phase; Clouds; Clouds and the Earth’s Radiant Energy System (CERES); ice; Ice clouds; Imaging radiometers; Infrared imaging; Infrared radiometers; liquids; meteorological data; Meteorological satellites; MODIS; Night; Orbits; Platforms; radiant energy; Radiation; Radiometry; Reflectance; Scanners; Spatial discrimination; Spatial resolution; Spectroradiometers; Trends; Water
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs15030578

Cloud properties are essential for the Clouds and the Earth’s Radiant Energy System (CERES) Project, enabling accurate interpretation of measured broadband radiances, providing a means to understand global cloud-radiation interactions, and constituting an important climate record. Producing consistent cloud retrievals across multiple platforms is critical for generating a multidecadal cloud and radiation record. Techniques used by CERES for retrievals from measurements by the MODerate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua platforms are adapted for the application to radiances from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership to continue the CERES record beyond the MODIS era. The algorithm adjustments account for spectral and channel differences, use revised reflectance models, and set new thresholds for detecting thin cirrus clouds at night. Cloud amounts from VIIRS are less than their MODIS counterparts by 0.016 during the day and 0.026 at night, but trend consistently over the 2012–2020 period. The VIIRS mean liquid water cloud fraction differs by ~0.01 from the MODIS amount. The average cloud heights from VIIRS differ from the MODIS heights by less than 0.2 km, except the VIIRS daytime ice cloud heights, which are 0.4 km higher. The mean VIIRS nonpolar optical depths are 17% (1%) larger (smaller) than those from MODIS for liquid (ice) clouds. The VIIRS cloud hydrometeor sizes are generally smaller than their MODIS counterparts. Discrepancies between the MODIS and VIIRS properties stem from spectral and spatial resolution differences, new tests at night, calibration inconsistencies, and new reflectance models. Many of those differences will be addressed in future editions.