SFB 641 The SFB Laboratory contributes 2 different techniques for the measurements of ice nuclei to VI Aerosol-Cloud Interaction: 1. 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

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

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

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

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)

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

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

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

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

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

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

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

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

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

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)

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