Rotational Raman lidar to measure the atmospheric temperature from the ground to 30 km

A lidar method using the anti-Stokes rotational lines of N₂ and O₂ Raman spectra to determine the temperature of the atmosphere up to 30 km is described. The method uses the variation with the temperature of the envelope of the intensities of the backscattered rotational Raman spectrum. For each temperature of the gas, the ratio of the fluxes through two narrow and close-by filters takes a definite value directly related to the temperature. The difficulty of eliminating the near-by contribution of the Mie backscattering was solved by doubling the filters to produce a rejection factor of 10⁺⁸ at the central wavelength. The validity of the method is illustrated by comparing a number of temperature profiles obtained simultaneously with radiosonde and by this new Raman lidar. The theoretical calculation of the method led to an analytic calibration function which, once adjusted with a radiosonde, can provide the temperature on successive days of measurement in the height range of 50 to 25 km