Craig A. Tepley, Jonathan Friedman, Raul Garcia, Shikha Raizada, and Eva Robles

Cornell University, NAIC Arecibo Observatory, HC-03 Box 53995, Arecibo, PR 00612

The Arecibo Observatory in Puerto Rico (18.35° N, 66.75° W) is a versatile tool used in a variety of research objectives that examine the characteristics of the low latitude atmosphere and ionosphere. Several radars and optical instruments, in place at the facility since the mid-1960's, are used by a number of visiting scientists every year. We will discuss a few of the many unique research programs that are currently underway at Arecibo, which study the structure, dynamics, and chemistry of the Earth's upper atmosphere.During the late 1980's we added novel lidar remote sensing capabilities to the existing complement of instrumentation at Arecibo. This gave us an ability to explore the fine details of the middle and lower atmosphere, a region that had been out of reach to other observational techniques until that time. When combined with radar and airglow observations, lidar measurements are a very powerful addition to probe the atmosphere as a coupled system.Our lidar research at Arecibo has only existed for a little more than a decade. It began with Rayleigh and Mie scatter observations of neutral density and aerosol concentration, as well as deriving the temperature of the atmosphere from the Rayleigh scattered signal. The program evolved to include resonance fluorescence lidar studies of metallic species present in the upper mesosphere. It includes observations of winds and temperature by direct sampling of the Doppler information inherent in the backscattered spectra. Finally, a new effort is underway to develop differential absorption lidar techniques to study the chemistry of various minor species of the stratosphere and troposphere.In this paper we will discuss the history, current research, and future direction of our lidar research at Arecibo.