Calibration and Validation of NUCAPS Infrared Surface Emissivity

NOAA NESDIS STAR maintains the NOAA Unique Combined Atmospheric Processing System (NUCAPS) Environmental Data Record (EDR) software for retrieval of atmospheric profiles of temperature, moisture and trace gasses as well as cloud-cleared radiances from Suomi-NPP and NOAA-20 CrIS and ATMS Sensor Data Records (SDRs). The Cal/Val of NUCAPS EDR products is ongoing at STAR to characterize product quality through comparison with external validation sources and to identify areas where improvements can be made. One of those areas of improvement has been identified by STAR to be the land surface infrared emissivity.

The UW CIMSS has a long history of development of global infrared databases leveraging satellite observations from the NASA EOS program and laboratory spectroscopy of terrestrial materials. The latest version of this global infrared database is the monthly Combined ASTER/MODIS Emissivity over Land (CAMEL) dataset which spans the time period 2000-2016 at 0.05 deg (5 km) grid spacing. A climatology and covariance has been developed both in the spectral domain and in the PC space of laboratory spectra.

Characterizing the infrared spectral variations among snow/ice, vegetated scenes, and bare soils are important for remote sensing of the atmospheric boundary layer and other weak atmospheric signals such as trace gas retrieval. This paper will describe the comparison of NUCAPS retrieved surface parameters with validation data including the CAMEL dataset. Proposed algorithm changes for future NUCAPS versions are described with an emphasis on improved performance of temperature and dewpoint profiles within the atmospheric boundary layer and subsequent improvement in thermodynamic stability parameters.