1. SFB 641
The SFB Laboratory contributes 2 different techniques for the measurements of ice nuclei to VI Aerosol-Cloud Interaction: in situ-measurements using the Fast Ice Nucleus CHamber = FINCH 2. IN-filter analysis by diffusion chamber/CCD = FRIDGE
Björn Nillius 2,Ulrich Bundke 1,Ruprecht Jaenicke 2,
Heinz Bingemer 1,Thomas Wetter1, Holger Klein 1
1) University of Frankfurt,2) University of Mainz

2. Ice Nucleus:
Operationally defined, as an aerosol particle upon which ice grows to macroscopic crystals, if exposed to supercooling and (ice supersaturation)

3. FINCH Mixing of 3 gas flows Total flow 50-90 l/min
Aerosol flow 5-10 l/min
Activation of IN at selected temperature and super-saturation (deposition freezing)
processing chamber of 1m
distinguish between ice crystals and super cooled water droplets

4. Detection
Backscattered light is detected and analyzed for the circular polarization under an angle of 115°
Separate detectors measure the two perpendicular linear polarized beams which are the result from the polarizing beam splitter
possibility to calculate the ratio of P44/P11 of the scattering matrix

5. Different ratio P44/P11 for supercooled droplets and ice crystals
(Y.-X. Hu et al. / Journal of Quantitative Spectroscopy
& Radiative Transfer 79–80 (2003) 757–764)
T =-12°C
Sice =1.8
Type (Ambient air)

6. First data from Cloud and Aerosol Characterisation Experiment CLACE 6
First field measurement
Data from 27th feb.- 13th mar 2007
~ 40 h of data are available
Measurements at total inlet and CVI ice inlet
Sphinx 3580 m

7. Measurement at total inlet (5 l/min)
Nearly const. aerosol distribution
Constant super-saturation
Decreasing temperature
activation of more at
lower temperature

8. Ascending cloud over the Aletsch glacier from the valley
Oncoming flow from south, south-west
Measurement at total inlet
Sample flow: 5 l/min

9. cloud CN number concentration in a range of 0.3µm and 0.8µm
Grimm OPC
J. Schneider, MPI Mainz
cloud

10. Measurement at CVI ice inlet
S. Mertes (IFT, Leipzig)

11. FRIDGE: Vaccuum diffusion chamber with CCD camera detection: a) counting of IN on filter, b) localise individual IN on substrate for ESEM analysis (TUD)

12. FRIDGE works, but not yet in routine
-15.3°C , S(Eis) = 122%
-20.8°C , S(Eis) = 127%
onset of ice nucleation:
FRIDGE vs. literature data

13. Contribution of FINCH and FRIDGE to Virtual Institute: laboratory experiments WP-L1 (and others ?) with the scientific objectives
efficiency of various aerosols as IN
quantify variation of IN efficiency by particle transformation
participate in experiments investigating competition of different aerosols as IN
intercalibrate our instruments and methods
provide a climatology of natural IN variability (IN monitoring at Taunus
Observatory and in Israel)
as input to sensitivity studies (modelling) of IN on cloud and precipitation
development

14. Team Ulrich Bundke (Pi) Ruprecht Jaenicke (Pi) Heinz Bingemer (Pi)
Vera Fischer
Laurin Herrmann
Rainer Rossberg
Robert Roeder
Thomas Wetter
Stephan Mertes (IFT Leipzig)
Johannes Schneider (MPI Mainz)
This work was supported by
Deutsche Forschungsgemeinschaft, SFB 641, A1

15. Ice detection
Discrimination between spherical and non-spherical particles using circular polarization
I0: Incident circular pol. beam
I: Backscattered beam
(Y.-X. Hu et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 79–80 (2003) 757–764)

16. Why we get so high differences in number concentration of CVI ice crystals and FINCH IN number concentration?
Only measurement of IN which are activated by deposition freezing (FINCH)
Ice crystals at the CVI ice inlet are activated by all freezing processes (deposition, immersion, condensation and contact freezing) and secondary ice formation
More comparison measurements are needed