CLACE GAW Plus

Duration: 2000-

Contact: Ernest Weingartner,

Background

Aerosols influence the atmospheric energy budget through direct and indirect effects:
  • Direct radiative effects include the scattering and absorption of solar radiation and the subsequent influence on planetary albedo and the climate system.
  • Indirect effects involve the influence of the aerosol on cloud properties, cloud lifetime and cloud cover through acting as cloud condensation nuclei (CCN) and ice nuclei (IN). Anthropogenic changes of the atmospheric aerosol loadings are expected to cause an overall negative climate forcing partially offsetting the positive forcing by greenhouse gases.
However, the aerosol effects are still poorly quantified due to the inhomogeneity of global aerosol loadings and chemical composition as well as the complexity of involved interactions and feedbacks. A major gap in the quantification of the aerosol indirect effect is the poor quantification of the global distribution of CCN.

Scope of project

Currently, we investigate microphysical properties of the prevailing liquid clouds at the Jungfraujoch station. Here we compare in situ measured ambient cloud droplet number concentrations with CCN number concentrations that were derived from laboratory measurements. These measurements will allow for the determination of the effective peak supersaturation in the prevailing ambient cloud which was responsible for the activation of aerosol particles to cloud droplets. These measurements represented an important part of a quality assurance procedure because the cloud droplet sampling process is critical and might bias the results derived from the laboratory based measurements. We seek for collaborations with the cloud modeling community because we believe that our observations have the potential to be successfully implemented in various models, contributing to a better quantification of the indirect aerosol effect on climate.

CLACE: Cloud and aerosol characterization experiments

Starting in 2000, these CLACE (cloud and aerosol characterization experiment) campaigns take place in regular intervals. These comprehensive aerosol - cloud interaction studies are conducted within national and international collaborations.
Year Campaign Season Institution Topic
2011 CLACE2011 Summer PSI Activation studies
2010 CLACE2010 Summer PSI Activation studies, hygroscopicity, chemical composition
      MeteoSwiss Wind field studies, remote sensing
      ETH Zürich Remote sensing, cloud droplet measurements
      FU Berlin Remote sensing
      BIRA Remote sensing
2008 CLACE2008 Spring PSI Activation studies, hygroscopicity, chemical composition
2007 CLACE 6.5 Summer PSI Activation studies, hygroscopicity, chemical composition
2007 CLACE 6 Winter PSI Activation studies, hygroscopicity, chemical composition
      Uni Manchester Cloud microphysics, chemical composition
      IFT Sampling of ice residuals
      MPI Mainz Chemical composition of ice residuals
      TU Darmstadt Offline analysis of ice residuals
      Uni Frankfurt IN Counter, determination of OC in IN
      ETH Zürich IN chamber, chemical composition
2006 CLACE 5 Winter PSI Activation studies, hygroscopicity, chemical composition
      IFT Sampling of ice residuals
      MPI Mainz Chemical composition of ice residuals
      TU Darmstadt Offline analysis of ice residuals
      Uni Frankfurt IN Counter, determination of OC in IN
      ETH Zürich IN chamber, chemical composition
2005 CLACE 4.5 Summer PSI Activation studies
2005 CLACE 4 Winter PSI Activation studies, hygroscopicity
      Uni Manchester Cloud microphysics, chemical composition
      IFT Sampling of ice residuals
      MPI Mainz Chemical composition of ice residuals
      TU Darmstadt Offline analysis of ice residuals
      Uni Frankfurt IN Counter, determination of OC in IN
2004 CLACE 3.5 Summer PSI Activation studies, hygroscopic properties
2004 CLACE 3 Winter PSI Activation studies, hygroscopic properties
      Uni Manchester Cloud microphysics, chemical composition
      IFT Sampling of ice residuals
      MPI Mainz Chemical composition of ice residuals
      TU Darmstadt Offline analysis of ice residuals
2002 CLACE 2 Summer PSI Activation studies, hygroscopic properties
      Uni Manchester Cloud microphysics, chemical composition
2000 CLACE 1 Winter PSI Activation studies, hygroscopic properties

Publications

See list of CLACE related publications