SFB 641 The SFB Laboratory contributes 2 different

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 Wetter 1, 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 supersaturation (deposition freezing) § processing chamber of 1 m § distinguish between ice crystals and super cooled water droplets

Detection § Backscattered light is detected 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 P 44/P 11 of the scattering matrix

(Y. -X. Hu et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 79– 80 (2003) 757– 764) § Different ratio P 44/P 11 for supercooled droplets and ice crystals T Sice Type =-12°C =1. 8 (Ambient air)

First data from Cloud and Aerosol Characterisation Experiment CLACE 6 § First field measurement § Data from 27 th feb. - 13 th 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

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% onset of ice nucleation: FRIDGE vs. literature data -20. 8°C , S(Eis) = 127%

Contribution of FINCH and FRIDGE to Virtual Institute: laboratory experiments WP-L 1 (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, A 1

Ice detection § Discrimination between spherical and nonspherical particles using circular polarization § I 0: 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