Verification and validation of an atmospheric boundary layer passive remote sensing technique using midwave infrared downwelling radiance

Passive radiometric remote sensing of the lower atmospheric is an attractive alternative to conventional techniques such as balloonsondes and active radiometric sensing with lidars. Measurements can be made with high sampling frequency, with complete safety and covertness, and with no loss in performance during day or night operation. A recently developed inversion algorithm generates vertical profiles of temperature and water vapor partial pressure from midwave infrared downwelling radiance to a ground based spectroradiometer. The technique is fast allowing real-time profile computation. Profiles up to 1 km altitude can be obtained for temperature and up to 0.5 to 1 km altitude for water vapor depending on the level of relative humidity. As with any new technique a verification and validation process must be performed to achieve acceptance. The verification is based on the fact that sound physical principles are employed with accepted databases (HITRAN spectroscopic database). The validation is based on comparisons with balloonsonde, MET tower, and Raman lidar measurements, and comparisons with MODTRAN 4 calculations of downwelling radiance using known profiles. An introduction to the inversion algorithm emphasizing verification is presented. This is followed by a discussion of the results from the comparison study.