The MODIS Precipitable Water product consists of column water-vapor amounts. During the daytime, a near-infrared algorithm is applied over clear land areas of the globe and above clouds over both land and ocean. Over clear ocean areas, water-vapor estimates are provided over the extended glint area. An infrared algorithm for deriving atmospheric profiles is also applied both day and night for Level-2. There are two MODIS Water Vapor data product files: MOD05_L2, containing data collected from the Terra platform, and MYD05_L2, containing data collected from the Aqua platform. The Level-2 data are generated at the 1-km spatial resolution of the MODIS instrument using the near-infrared algorithm during the day, and at 5x5 1-km pixel resolution both day and night using the infra-red algorithm when at least nine FOVs are cloud free. The infrared-derived precipitable water vapor is generated as one component of product MOD07, and simply added to product MOD05 for convenience. The solar retrieval algorithm relies on observations of water-vapor attenuation of reflected solar radiation in the near-infrared MODIS channels so that the product is produced only over areas where there is a reflective surface in the near IR.
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- Digital Object Identifier (DOI) Reference
|Total Precipitable Water Vapor 5-Min L2 Swath 1km and 5km||
The Suomi National Polar-orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) is not inherently a sounding instrument but does afford some spectral bands to help integrate total column water vapor. In order to compensate for its lack of water vapor absorption channels, this product benefits from water vapor soundings from two additional sounder instruments aboard the Suomi NPP platform: Advanced Technology Microwave Sounder (ATMS) and Cross-track Infrared Sounder (CrIS). The water vapor product is derived by adapting the MODIS atmospheric profile algorithm and assisted by the sounding-based measurements from the two co-existing instruments on the same platform.
The Level-2 6-minute product provides clear-sky total column water vapor (TPW) properties that portrays global moisture at 750 meters spatial resolution. In addition to the Level-2 product, two Level-3 products, a daily composite, and a monthly composite, both at 0.5 degrees, also exist.
|VIIRS Product Name||Suomi NPP|
|Level-2 Water Vapor Products 6-min Swath 750m||
|Level-3 Daily Mean Water Vapor Global 0.5x0.5 Degree Grid||
|Level-3 Monthly Mean Water Vapor Global 0.5x0.5 Degree Grid||