Performance capabilities of middle-atmosphere temperature lidars: Comparison of Na, Fe, K, Ca, Ca⁺, and Rayleigh systems

The measurement accuracies of modern resonance fluorescence and Rayleigh temperature lidars are limited primarily by photon noise. The narrowband three-frequency fluorescence technique is shown to perform within a few decibels of the theoretical optimum at night for both temperature and wind observations. These systems also exhibit good performance during the day because the fluorescence wavelengths of Na, Fe, K, Ca, and Ca⁺ all correspond to strong solar Fraunhofer lines, where sky brightness is attenuated by a factor of 5 or more. Whereas Na systems achieve the highest signal-to-noise ratios for mesopause region observations (80-105 km), the three-frequency Fe system is attractive because it performs well as both a fluorescence and a Rayleigh lidar throughout the middle atmosphere at approximately 25-110 km.