Temperature is also measured using Rayleigh-scattering from air molecules. Rayleigh-scattered light is responsible for the blue sky we observe on a clear day. An explaination of the z 2 factor can be found here. Once the density profile is known the temperature can be found by Assuming hydrostatic equilibrium . Atmospheric pressure decreases with height in the atmosphere.
Gravity is the force which hold the atmosphere in place.
By about 15 km below the start of the integration the effect is negligible. The mercury is put in a container and spun, in our case at 6 RPM, to achieve a parabolic surface which is ideal for lidar measurements. A schematic of a LMT system shows the idea is a simple one in principle. This large mirror, combined with the laser system shown above , allows our system to measure changes in temperature due to waves in a matter of minutes. Here is an example of a nigthly-averaged temperature profile from the Purple Crow Lidar compared to a model atmosphere.