CrIMSS Temperature and Water Vapor Retrieval Validation Using ARM Site Atmospheric State Best Estimates and GPS RO COSMIC

The Cross-Track Infrared and Microwave Sounder Suite (CrIMSS), onboard the S-NPP satellite, is comprised of the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS) and represents a new generation of satellite-based atmospheric sounders capable of high vertical resolution profiles of temperature and water vapor. Given the high accuracy retrieval goals of CrIMSS (1 degree Kelvin accuracy for 1 km layers in the troposphere and moisture profiles accurate to 15 percent for 2 km layers) careful and detailed validation is needed. This ongoing and collaborative effort, which began in July of 2012, involves the Atmospheric Radiation Measurement (ARM) program, UW – Madison, and the Joint Polar Satellite System (JPSS) project. In this arrangement, radiosondes are launched coincident with the S-NPP satellite overpasses of the ARM sites located at Eastern North Atlantic (ENA), North Slope of Alaska (NSA), Southern Great Plains (SGP), and Tropical West Pacific at Manus (TWP). Combined with other ARM data, an assessment of the radiosonde data quality is performed and post-processing corrections are applied producing an ARM site best estimate (BE) product. This validation data set is a well-characterized ensemble of temperature and water vapor profiles, which is essential for assessment of the advanced sounder products. Comparisons are presented between the BE of the atmospheric state and retrievals from the Global Data Assimilation System (GDAS) and the NOAA Unique CrIS ATMS Processing System (NUCAPS).

In measuring upper-tropospheric and lower-stratospheric temperatures, radiosondes are often not best suited given that the measurement accuracy decreases and often the radiosonde itself fails to reach these heights. The Global Positioning System (GPS) Radio Occultation (RO) technique is a more recent method that offers the potential to produce climate-quality measurements with SI traceability in this region of the atmosphere. An evaluation of NUCAPS temperature retrievals within the stratosphere was made using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO dry temperature products. A limited number of matchup cases (within 100km and 1.5 hours) between ARM BE radiosonde, NUCAPS, and COSMIC profiles were found and analyzed. Analyses were also performed for comparisons between COSMIC, NUCAPS and ARM radiosonde temperatures over a 3-year time period for the NSA, SGP, and TWP ARM sites. Bias statistics of the differences showed that RO is in good, <0.5K agreement with the radiosondes over the vertical range 200-30hPa and supports the claim that RO can be used a validation point for hyperspectral IR sounder products.