M. Posyniak

Particle size distribution retrieval from multiwavelength lidar signals for droplet aerosol

A method of retrieval of the aerosol particle size distribution (APSD) from multiwavelength lidar signals is presented. Assumed distribution (usually a bimodal combination of lognormal functions) with a few free parameters is directly substituted into the lidar equations. The minimization technique allows one to find the parameters that provide the best fit of the assumed APSD by comparison of theoretically generated and experimental signals. Prior knowledge of the lidar ratio is not required. The approach was tested on a typical synthetic APSD consisting of spherical droplets. Comparison of lidar measurements with results from a condensation particle counter was also performed. For signals registered at 3-5 wavelengths from the UV to the near IR a satisfactory retrieval of synthetic APSD is possible for the particles within the 100-3000 nm range.

Study of Vertical Structure of Aerosol Optical Properties with Sun Photometers and Ceilometer During the MACRON Campaign in 2007

This paper presents the measurements of a vertical structure of aerosol optical properties performed during the MACRON (Maritime Aerosol, Clouds and Radiation Observation in Norway) campaign, which took place in July and August 2007 at ALOMAR observatory on Andøya island (69.279°N, 16.009°E, elevation 380 m a.s.l.). The mean value of the aerosol optical thickness (AOT) at 500 nm during campaign was 0.12. Significant increase of the AOT above longtime mean value was observed on 7 and 8 August 2007 when the AOT exceeded 0.4 at 500 nm. Analyses of back trajectories show the aerosol transported from over Africa and Central Europe. The aerosol extinction coefficient obtained from the synergy of ceilometer and sun photometer observations reached 0.05–0.08 km−1 (at 1064 nm) in the dust layer. The single scattering albedo at the ALOMAR observatory decreased during the dust episode to 0.93–0.94, which indicates some absorptive aerosols in the lower PBL.

Aerosol investigation with multiwavelength lidar

Results of measurements of atmospheric aerosol performed with multiwavelength lidar are presented. An approach to retrieve profiles of aerosol particle size distribution was elaborated. It consists in direct fit of predefined distribution (usually combination of lognormal functions with a few free parameters) to the experimental signals. The approach was used for retrieving marine aerosol distributions. Studies of behavior of the particles at the cumulus cloud base were performed as well. There the assumptions based on Twomeys model of the adiabatic parcel were used to support the retrieving technique which was adopted to analyze lidar profiles (at 355, 532 and 1064 nm wavelengths) registered in the region of the base of small warm cumulus clouds. Size distribution profiles and changes of particle effective radius within the range of 0.5 - 3 μm were discussed.

Multiwavelength micropulse lidar in atmospheric aerosol study: signal processing

Multiwavelength micropulse lidar (MML) designed for continuous optical sounding of the atmosphere is presented. A specific signal processing technique applying two directional Kalman filtering is introduced in order to enhance signal to noise ratio. Application of this technique is illustrated with profiles collected in course of COAST 2009 and WRNP 2010 research campaigns.

Simple and safe short-range lidar system for undergraduate laboratory

A simple and safe lidar system based on a nitrogen laser (337.1 nm) is described. The setup permits undergraduates to learn the principles and applications of the lidar technique. The apparatus is used for exercises about measurements of distance to objects, the determination of light velocity as well as about retrieving the back-scatter coefficient of a water aerosol cloud. The system may also be used for demonstrating the principle of fluorescence lidar.