B. Stein

Derivation of Mount Pinatubo stratospheric aerosol mean size distribution by means of a multiwavelength lidar

A multiwavelength lidar operated in Sodankyla, Finland, during the European Arctic Stratospheric Ozone Experiment (December 1991-March 1992). It produced vertical profiles of stratospheric aerosols at four wavelengths. The determination of aerosol mean size distribution has been performed by use of extinction/backscattering ratios as obtained from lidar data processing at 355, 352, and 750 nm. Lognormal distributions of sulfuric particles with mode radius of r(m) = 0.12-0.25 µm and corresponding widths of s = 2-1.6 have been retrieved as best fits of experimental data, in good agreement with in situ measurements. A successful attempt to derive bimodal log-normal distributions is also described, together with the experimental and theoretical problems involved.

Stratospheric aerosol size distributions from multispectral lidar measurements at Sodankylä during EASOE

This paper presents results from lidar measurements made at Sodankyla (67[degrees]N) of stratospheric aerosols during EASOE. The lidar was capable to resolving size distributions into the micron size range, and by polarization techniques distinguishing PSC formations. Volcanic gas source aerosols were observed to be .1 to .3 microns in mean radius between 17 and 22 km, and larger below this altitude.

Airborne and Ground-Based Measurements Using a High-Performance Raman Lidar

Abstract A high-performance Raman lidar operating in the UV portion of the spectrum has been used to acquire, for the first time using a single lidar, simultaneous airborne profiles of the water vapor mixing ratio, aerosol backscatter, aerosol extinction, aerosol depolarization and research mode measurements of cloud liquid water, cloud droplet radius, and number density. The Raman Airborne Spectroscopic Lidar (RASL) system was installed in a Beechcraft King Air B200 aircraft and was flown over the mid-Atlantic United States during July–August 2007 at altitudes ranging between 5 and 8 km. During these flights, despite suboptimal laser performance and subaperture use of the telescope, all RASL measurement expectations were met, except that of aerosol extinction. Following the Water Vapor Validation Experiment—Satellite/Sondes (WAVES_2007) field campaign in the summer of 2007, RASL was installed in a mobile trailer for ground-based use during the Measurements of Humidity and Validation Experiment (MOHAVE-II...

A four-wavelength depolarization backscattering LIDAR for polar stratospheric cloud monitoring

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.

Effects of stratospheric aerosols from the Mt. Pinatubo eruption on ozone measurements at Sodankylä, Finland in 1991/92

This article reports on column ozone measurements made from Sodankyla, (67[degrees]N), during the winter of 1991-1992. These measurements have been made with a Brewer spectrophotometer, and a SAOZ instrument. The results are correlated with TOMS data also. A strong sensitivity to light scattering due to atmospheric aerosols has been shown. When airmass factors are adjusted into the measurements, then the measurements are better correlated between themselves.

Aerosol size distribution measurements using a multispectral lidar system

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.

Lidar observation of spherical particles in a −65° cold cirrus observed above Sodankyla (Finland) during S.E.S.A.M.E.

Abstract The absence of LIDAR depolarization in a polar cirrus observed above Sodankyla (Finland) showed the presence of spherical particles at −65°C. The presence of pure liquid water is excluded, since homogeneous freezing should occur at or above −40°C. The cirrus layer was detected at the tropopause, during the horizontal and vertical advection above northern Scandinavia of warm and wet oceanic air. Two alternative explanations are suggested, the first one involving the presence of large, deliquescent tropospheric CN, freezing at very low temperature, and the second one involving the presence of metastable, spherical ice-particles produced in the fast adiabatic cooling of the airmasses. The second hypothesis is less reasonable because the absence of depolarized LIDAR signal implies a strict cylindrical symmetry in the particles, a symmetry that is difficult to maintain during the freezing process.

Error analysis of restoring stratospheric aerosol parameters from single frequency lidar sounding

An algorithm for restoring stratospheric backscatter coefficients from ground-based lidar measurement is proposed. Error sources of the algorithm are analyzed including the boundary condition, the molecular backscatter coefficients, and the influence of the aerosol light extinction.

Trajectory studies of polar stratospheric cloud lidar observations at Sodankylä (Finland) during SESAME : Comparison with box model results of particle evolution

Polar stratospheric clouds (PSC) were observed with the multi-wavelength lidar of the MOANA project (Modelling and Observations of Aerosols in the Northern Atmosphere) during SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment). The physical state, liquid or solid, of the cloud particles can be inferred from the lidar data. Using isentropic back-trajectories to obtain the thermal history of the sampled air masses, it is possible to reconcile most of the observations with current ideas on PSC formation and evolution. When the cloud particles were identified as liquid, changes in the size distribution of the droplets along the trajectory were calculated using a micro-physical box model. Backscatter ratios calculated from the size distributions are in broad agreement with the lidar data, giving confidence in current understanding of the evolution of ternary solution (H2SO4, HNO3 and H2O) droplets.Results from two soundings are shown which bear on the problem of the formation of solid particles. In the first, solid particles were detected. The air mass had cooled to the frost point 12 hours earlier. In the second no solid particles were detected although the air temperature was below the nitric acid trihydrate existence point, and had decreased by 12K in the previous 14 hours.

Polar Stratospheric Cloud Measurements by Multispectral Lidar at Sodankyla in Winter 1994/95

Lidar measurements at 4 wavelengths and two polarizations were performed during the SESAME campaign in Sodankyla, Finland (67.37N, 26.65E). Using the wavelength dependence of the particle scattering the aerosol size distribution and the refractive index of the PSC particles were retrieved. A liquid PSC with a refractive index of 1.36 could be observed. We assume that this PSC consists of ternary solution particles in contradiction to the NAT-hypothesis.