Lidar Studies of Upper Atmosphere Composition and Dynamics

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The use of Lidar techniques has led to important advances in measuring properties of the atmosphere below 110 km altitude. This is a region where there is little return from radar probing, especially at night. The lidar provides density data from the backscattering on air molecules, and thus measures the background density, density waves propagating through the medium, and from the rate of density decrease with height, provides data on temperature. Lidars can be tuned to wavelengths resonantly scattered by specific atoms, and for sodium Lidars the changes in height and vertical profile are sensitive indicators of vertical velocity and of the passage of waves through the region 80-100 km. This award is for upgrading and operating two lidars in a series of cooperative campaigns with other scientists using radio and other optical techniques to probe the atmosphere. The capability will be added to measure resonant scattering from the layers of neutral iron and calcium and ionized calcium, and to make daytime measurements with the newer high power lidar.