1064 nm rotational Raman lidar for particle extinction and lidar-ratio profiling: cirrus case study

摘要

For the first time, vertical profiles of the 1064 nm particle extinctioncoefficient obtained from Raman lidar observations at 1058 nm (nitrogen andoxygen rotational Raman backscatter) are presented. We applied the newtechnique in the framework of test measurements and performed several cirrusobservations of particle backscatter and extinction coefficients, andcorresponding extinction-to-backscatter ratios at the wavelengths of 355,532, and 1064 nm. The cirrus backscatter coefficients were found to be equalfor all three wavelengths keeping the retrieval uncertainties in mind. Themultiple-scattering-corrected cirrus extinction coefficients at 355 nm wereon average about 20–30 % lower than the ones for 532 and 1064 nm. Thecirrus-mean extinction-to-backscatter ratio (lidar ratio) was 31 ± 5 sr(355 nm), 36 ± 5 sr (532 nm), and 38 ± 5 sr (1064 nm) in this singlestudy. We further discussed the requirements needed to obtain aerosolextinction profiles in the lower troposphere at 1064 nm with good accuracy(20 % relative uncertainty) and appropriate temporal and vertical resolution.