Airborn measurements of IfT Leipzig

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1. Contact

Dr. Manfred Wendisch
IfT Leipzig
Permoser Str. 15
04318 Leipzig Germany

Tel.: +49 341 235 2469
Fax.: +49 341 235 2361
E- mail: wendisch@tropos.de
Homepage: http://www.tropos.de

2. Short Description

Airplane "D-GERY" type PARTENAVIA is operated by the IfT for the whole BBC campaign with meteorological and avionic sensors, an Albedometer for radiation measurements, a Particle Volume Monitor (PVM), a Fast Forward Scattering Spectrometer Probe (FFSSP) and an Optical array probe (OPC, provided by GKSS) for microphysical cloud characterization. Optionally, instruments for measuring aerosol size distribution and scattering and absorption coefficients can be mounted.

The albedometer measures spectral upward and downward irradiances in the range from 400 nm to 1000 nm. The optical inlets (cosine diffusers) of both sensors are mounted at the top and the bottom of the aircraft and are actively stabilized in a horizontal position. They are connected to a spectrometer (fixed grating with 1024 pixel diode array) by optical fibers. The time resolution is up to 1 Hz.

The Fast FSSP measures water droplets (range 1-50 µm) passing by a laser beam. The forward scattering signal of every individual droplet passing the sample volume are stored, along with the respective arrival time and droplet duration. This allows drop size distribution measurements with a high time resolution.

The PVM measures the liquid water content and the effective surface of a droplet population being exposed to a laser beam. This is being done by using special spatial filters. The effective radius of the population can be calculated from the two measured quantities.

3. Goals within 4D-clouds

In-situ measurement of microphysical cloud parameters such as size distribution of water droplets in a range of 1 µm to 6 mm, liquid water content and effective drop radius with high time resolution are provided as input parameters for more dimensional cloud characterization and validation of remote sensing cloud measurements. Highly resolved microphysical data is used to study turbulence and scaling laws in cloud fields. From spectral radiation measurements (albedometer) the influence of cloud inhomogeneities on radiation is investigated. For cloudless days, aerosol instruments and the albedometer are flewn.

4. Instrument Specifications

4.1 Albedometer

Measurement quantity Upward and downward Spectral Irradiance [W/m²nm]
Range ~ 400 to 1000 nm
Resolution Up to 1024 channels
Sample frequency Up to 1 Hz, varying time resolution for Quicklooks
Horizontal stabilization Within ±6° roll and/or pitch
Accuracy of hor. stab. Better than 0.3°
Manufacturer Meteo consult, Frankfurt, Germany

4.2 Fast FSSP

Measurement quantity Drop size distribution [#/cm³µm]
Resolution 1-50 µm in 256 size classes
Sample frequency Every droplet, for Quicklooks 1 Hz
Manufacturer CNRM, Toulouse, France

4.3 PVM

Measurement quantity Liquid water content [g/m³]; Effective Radius [µm]
Resolution LWC: 0.005 g/m³
Sample frequency 200 Hz, for Quicklooks 1 Hz
Manufacturer Gerber Scientific, USA

4.4 OAP

Same as the PMS OAP 2D2-C onboard the Merlin.

5. Data

For the database, 1 Hz data are provided for OAP (GKSS), Fast FSSP, PVM and meteorological data. For the albedometer, time resolution is up to 1 Hz. In principle, more detailed information (PVM: 200 Hz data, FFSSP: droplet information) can be obtained directly from Sebastian Schmidt, schmidt@tropos.de or Manfred Wendisch, wendisch@tropos.de.

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