Because of this, our understanding of buoyancy waves is extremely important to our understanding of the atmosphere as a whole. Some clouds are too thin to be seen with the naked eye. A lidar can detect such clouds. It operates like a radar but uses visible or infrared waves in place of radio waves, and can observe things that a radar can not. Arecibo scientists also study the atmosphere using optical radars known as lidars.
Lidars can measure atmospheric density, temperature, winds, as well as dust and pollutants.
The extraterrestrial metal atoms deposited in the upper atmosphere by meteors can also be observed by the Arecibo lidars. A map of atmospheric density seen by lidar overlaid with horizontal wind measurements made by radar. The thick, bright layers at the left of the plot are clouds that resulted from a thunderstorm. The thin layer in the middle of the plot is due to clouds which cannot be seen by the naked eye. The lidar provides crucial information that the radar cannot obtain.