Experimental Validation of a Forward Looking Interferometer for Detection of Clear Air Turbulence Due to Mountain Waves

The Forward-Looking Interferometer (FLI) is an airborne sensor concept for detection and estimation of potential atmospheric hazards to aircraft. To be commercially viable such a sensor should address multiple hazards to justify the costs of development, certification, installation, training, and maintenance. The FLI concept is based on high-resolution infrared Fourier Transform Spectrometry (FTS) technologies that have been developed for satellite remote sensing. These technologies have also been applied to the detection of aerosols and gases for other purposes. The FLI is being evaluated for its potential to address multiple hazards, during all phases of flight, including clear air turbulence (CAT), volcanic ash, wake vortices, low slant range visibility, dry wind shear, and icing. In addition, the FLI is being evaluated for its potential to detect hazardous runway conditions during landing, such as wet or icy asphalt or concrete. The validation of model-based instrument and hazard simulation results is accomplished by comparing predicted performance against empirical data. Models for FLI measurables for mountain wave turbulence were developed during the previous phases of the project. This paper presents a follow-on analysis to the paper, "Hyperspectral Image Turbulence Measurements of the Atmosphere" regarding the atmospheric data collected over the Colorado Rockies, near Boulder, CO. Brightness temperature differences were used in the identification of clouds, as opposed to spectral features of clouds versus sky. When the clouds are removed using the cloud brightness temperature threshold values, the variability is almost eliminated.