Atmospheric temperature measurements made by rotational Raman scattering

Rotational Raman scattering of light from the second harmonic of a Nd:YAG laser is used to measure atmospheric temperature at altitudes of 3 to 20 km. The method relies on taking the ratio of light passed by two filters that differ slightly in their passbands, and is therefore insensitive to variations in atmospheric transmission. The calibration of the experiment relies on only spectroscopic measurements and not on normalizing to nearby radiosondes, as has been the previous practice with this kind of experiment. Comparisons with radiosonde profiles show excellent agreement to within the precision of the measurements and the variability of the atmosphere. The main application of the experiment lies in its ability to measure a time series of temperature profiles with good height resolution throughout a night. Examples of such series that show the passage of a tropopause fold above the lidar are presented.