Towards Continuity in Cloud Top Height from MODIS to the Joint Polar Satellite System (JPSS) Polar-Orbiting Sensors

This talk presents the progress and issues involved with developing a continuous record of cloud properties, such as cloud-top height (CTH), from the MODIS sensor on the NASA Terra/Aqua platforms to the VIIRS (Visible Infrared Imaging Radiometer Suite) and CrIS (Cross-track Infrared Sounder) sensors that are on the current Suomi-NPP and future NOAA JPSS (Joint Polar Satellite System) polar-orbiting platforms. The MODIS measurements include infrared (IR) window radiances at 8.5-, 11- and 12-μm and four 15-μm channels in the broad CO₂ absorption band. For MODIS, the cloud top pressure/height and emissivity are derived using a technique in which the strength is in retrievals for mid-to-high clouds but less so for low clouds where there is little thermal contrast with the surface. Our goal is to extend these cloud properties to the JPSS era as seamlessly as possible. There is one large drawback to consider: VIIRS has no infrared (IR) absorption channels. The lack of at least one IR absorption channel on VIIRS degrades the accuracy of the CTH. To mitigate this problem, our approach is to construct a 13.3-μm channel from a combination of VIIRS and CrIS. This data fusion approach involves using the high spatial resolution VIIRS IR window channels in combination with a lower spatial resolution 13.3-μm channel derived using CrIS high spectral resolution measurements. The end result is a 13.3-μm channel at the VIIRS pixel spatial resolution of 750 m (i.e., M-band resolution). The radiometric accuracy of this approach was tested using MODIS and AIRS, and found to be within 1-2%. An optimal estimation approach is adopted to derive CTH based on the availability of the 11-, 12, and 13.3-μm channels that shows potential for achieving continuity between MODIS and Suomi-NPP. Since future platforms will likely continue with a pairing of an imager and hyperspectral sounder, this work lays the foundation for cloud product continuity. We will show global one day CTH results and uncertainties for cloud height based on MODIS to VIIRS/CrIS measurements.