Class presentation Applications of the Helsinki Test Bed CL31 Ceilometer data Anu-Maija Sundström University of Helsinki Division of Atmospheric Sciences

”Lidar in Aerosol Research””Lidar in Aerosol Research” FMI, Vaisala, University of Helsinki Funded by TEKES ( the Finnish Funding Agency for Technology ) Jan Dec 2005 Vaisala CL31 ceilometer at Kumpula Campus Two main topicsTwo main topics Particles physical modeling 2. ”Ceilometer climatology” and relation to particle concentrations Background

Lidar measurements CL31 vertically pointing elastic backscatter lidar, operates at 910 nm wavelenght Lidar ”sees” everything within the measurement volume, i.e. air molecules, aerosols, and hydrometeors limitations to see very small particles To study only the aerosol contribution of the backscattered signal we need to exclude Rain data (also ice) The molecular scattering A reliable rain data filtering method is needed

To test and improve the rain data filtering method threshold value in relative humidity present weather sensor threshold value in a vertical average of lidar backscattering threshold value in temporal variation of lidar backscattering To study the relation between PM10 concentrations and lidar backscattering at different locations E.g. how much the local effects affect results Objectives

From Test Bed: CL31 backscattering profiles from various stations and Meteorological data (rain, wind) PM10 concentration Possibly also other profilers Important issues: CL31 device settings The metadata from the TB-stations Data

An Example Vallila Test Bed Station , 1 h averages of PM10 concentrations Temporal variation of modeled and measured backscattering coefficient at Kumpula Vertical mixing ? What is the signal from Vallila CL31?...