Incoherent Doppler LIDAR for continuous measurement of wind and aerosol profiles

The University of Michigan Space Research Laboratory has developed a mobile, high spectral resolution incoherent Doppler lidar capable of measuring wind and aerosol loading profiles in the troposphere and lower stratosphere. The system uses a 3 Watt pulsed frequency doubled Nd:YAG laser operating at 532 nm. The backscattered signal is collected by a 44.4 cm diameter Newtonian telescope. A two axis mirror scanning system allows the instrument to achieve full sky coverage. Active feedback control of key instrument elements provides an overall instrument stability of better than 1 m/s. A pair of Fabry-Perot interferometers in combination with a narrowband (0.05 nm) interference filter are used to filter daylight background and provide a high spectral resolving element to measure the Doppler shift. In addition, the aerosol and molecular scattered components of the signal can be separated, giving a measure of the relative aerosol loading. Measurements have been made day and night in the boundary layer with vertical resolution of 100 meters and a temporal resolution of approximately 6 minutes. Accuracy of the wind velocity is on the order of 1-2 m/s in the boundary layer. Continuous measurements on this temporal scale should prove highly useful in parameterizing atmospheric aerosol movement, cloud evolution, and wind field variability.