Water vapor exists in the atmosphere only in small amounts, but it plays a big role in many important atmospheric processes. For example, water vapor is a fundamental part of the atmospheric energy budget, global water cycle, atmospheric chemistry, and transport processes of pollution. A lidar is an instrument that uses short pulses of laser light to detect particles or gases in the atmosphere, like a radar bounces radio waves off rain drops in clouds. A telescope collects and measures reflected laser radiation, like a radar dish collects the radar signal, leading to a profile of the atmosphere's structure along the path of the laser beam. Different types of lidars measure different atmospheric properties.
Scientists know that different molecules absorb light only at certain wavelengths.
They can then tune laser pulses to different wavelengths to target the type of atmospheric molecule they want to study using the DIAL method. To measure water vapor, aerosols, and clouds, researchers use the LASE system. Scientists developed LASE as a prototype for a space-borne DIAL system. Since 1995 researchers have used LASE on six different major atmospheric field investigations. LASE uses the DIAL technique to determine vertical profiles of water vapor in the lower atmosphere.