Class presentation 16.2.2007

Applications of the Helsinki Applications of the Helsinki Test Bed CL31 Ceilometer Test Bed CL31 Ceilometer

datadata

Anu-Maija Sundström

University of HelsinkiDivision 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 2005- Dec 2005

• Vaisala CL31 ceilometer at Kumpula Campus

• Two main topicsTwo main topics

1.1. Particles physical modeling

2. ”Ceilometer climatology” and relation to particle concentrations

BackgroundBackground

Lidar measurementsLidar 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

ObjectivesObjectives

From Test Bed:From Test Bed:

• CL31 backscattering profiles from various stations and

• Meteorological data (rain, wind)

• PM10 concentration

• Possibly also other profilers

Important issues:Important issues:

• CL31 device settings

• The metadata from the TB-stations

DataData

An ExampleAn Example

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Time [h]

PM

10 [

10-6

gm

-3]

Vallila Test Bed Station 20.8.2005, 1 h averages of PM10 concentrations

Temporal variation of modeled and measured backscattering coefficient at Kumpula 20.8.2005

• Vertical mixing ?

• What is the signal from Vallila CL31?

•...