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A four wavelength backscattering depolarization LIDAR designed for polar stratospheric cloud and stratospheric aerosol measurement is described. The system uses the following wavelengths: 355 nm, 532 nm, 750 nm, and 850 nm. These wavelengths, obtained by means of the third- and second-harmonic of a Nd: YAG laser and by means of a tunable Ti: Sapphire laser, are chosen in a way to better characterize the particel size of such stratospheric aerosols. They are not emitted simultaneously as the LIDAR system is designed with only two detection channels permitting to detect, in the analog and in the photon counting mode, both the direct and the depolarized backscattered signal. The system has been operational in northern Finland since the end of November 1991.

Consideration is given to a novel inversion algorithm to determine the aerosol size distribution from lidar signals obtained at several wavelengths. This algorithm is based on a nonlinear fit of the backscattered measurements using a set of predetermined functions. Size distribution profiles of tropospheric aerosols in different meteorological conditions - clear, hazy, and cloudy atmosphere - are determined on the basis of lidar measurements made in central Switzerland, which is characterized by a specific microclimate. Measurements of stratospheric clouds and aerosols created by the Pinatubo eruption were measured above Berlin and Sodankyla, Finland. These measurements are used to characterize the size distribution of these volcanic aerosols in order to estimate their influence on radiative transfer.

Since January 1988 an Italian backscattering Lidar has been operating in Antarctica, at the Italian base of Terra Nova Bay during the summer 1988 and now at the French base of Dumont d’Urville. The system was built by the research group of IROE of CNR, within a broad research program on atmospheric studies carried out by the Italian National Program for Antarctic Research. Among the principal objectives of this program are to contribute understanding of the Ozone Hole problem and to characterize the radiative properties of clouds by means of Lidar, IR radiometry, local meteorological data and satellite data, in order to better understand the role of clouds in the radiative budget of the planet. A complex DIAL system, to carry out ozone concentration measurements in the Ozone Hole, is presently being built under the Italian-French cooperative program for Antarctica, while an automated Nd-YAG diode pumped Lidar is being designed to operate semiautomatically in an Antarctic winter base, maybe at Dome C, which will be located on the Antarctic Plateau, at 3250 meters altitude.

An elastic backscattering lidar and initial results are described. The lidar system has been designed to operate in Antarctica for the Italian National Programme for Antarctic Research. The first field trials were held during the period from 31 December 1987 to 10 February 1988. Data were collected for both tropospheric and stratospheric atmospheric parameters. Tropospheric measurements included the cloud base, optical depth, extinction and backscattering coefficients for clouds, whereas aerosols and the molecular atmosphere were monitored in the stratosphere. The lidar system was also tested for the determination of temperature and density in ranges up to 40 km. Preliminary results of the lidar measurements carried out at Terra Nova Bay are presented. The lidar system is composed of a Nd−YAG laser, a Newtonian telescope and two receiving channels with computer-controlled data acquisition and display equipment. The system is operated in a mobile container specifically designed for the Antarctic environment.

Differential insolation generally strongly influences the spectral responses of woody areas distributed over hills and mountains, making them difficult to discriminate by means of remote sensing te...