Środowiskowe Seminarium Fizyki Atmosfery

Multi-wavelength Raman and High Spectral Resolution aerosol lidars are recognized as powerful tools for aerosol characterization. The height resolved spectra of particle backscattering, extinction and depolarization provided by such lidars are important for Earth radiation budget studies and can also be used for aerosol classification. But even more attractive is the possibility of inverting lidar measurements to height profiles of particle physical properties, such as size, concentration and complex refractive index. During the last decade numerous theoretical and experimental studies have been performed attempting to realize such inversions and the results obtained look rather promising. However, before applying multi-wavelength technology to regular aerosol observations, numerous issues should be resolved. First of all, the number of lidar measurements is very limited, typically only three backscattering and two extinction measurements are available. Thus the inverse problem is under-determined and the family of solutions obtained using different initial guesses about particle complex refractive index and inversion interval should be considered. Second, the particles may be of irregular shape, the complex refractive index may be spectrally dependent and the aerosols may be represented by external or internal mixtures. And finally, the retrieval algorithm should be fast to manage large volumes of data. This talk is intended to analyze the uncertainties arising from the factors mentioned above, to present different approaches for inversion of lidar measurements and to apply these algorithms to long-term lidar observations. Retrieved time series of particle physical parameters are compared with column integrated values provided by AERONET. The results of the application of an algorithm based on a model of randomly oriented spheroids to the inversion of multi-wavelength lidar dust measurements will be also discussed.