Pure rotational Raman lidar based on wavelength division multiplexing technique for temperature profiling of the troposphere

摘要

A new high-accuracy pure rotational Raman (PRR) lidar system at a laser wavelength of 532.25 nm, based on a technique of wavelength division multiplexing (WDM), has been designed for profiling the atmospheric temperature of the low troposphere. A special WDM, which was usually used in fiber communication field, is designed to separate two PRR signals of N_2 and O_2 for temperature retrieval, and to simultaneously block Mie- and Rayleigh-scattering signals with a rejection rate of large than 10~7. A numerical calculation is simulated to verify the feasibility of the lidar system, and the results showed that the PRR lidar based on spectroscopic characteristic of the WDM is capable of measuring the atmospheric temperature vertical profiles in the low troposphere, and a statistical temperature error less then 1K was achieved up to a height of 3.3 km and 5 km for daytime and nighttime measurement, respectively, under conditions of 300 mJ laser energy, 25-cm-diameter telescope, 10 min observation time, solar radiance of 3 × 10~8 Wm~(-2)sr~(-1)nm~(-1) and atmospheric backscattering ratio less then 3.4.