Cirrus Clouds and Water Vapor

Cirrus clouds exist in the upper troposphere, at altitudes between about 7 to 17 km. They can appear as wide sheets, wispy filaments, or as sub-visible cloud layers. Because cirrus clouds cover up to 30% of the Earth, they play an important role in atmospheric chemistry and climate. First, Cirrus clouds have a net heating effect on the Earth.

Second, cirrus clouds dehydrate the atmosphere and influence the water vapor in the upper troposphere and stratosphere, which is one of the most important greenhouse gases. Radiative properties and dehydration potential of cirrus clouds depend critically on the particles size and number density of ice particles which are determined by meteorological conditions (water vapor, temperature and small scale temperature fluctuation) and the atmospheric number density of heterogeneous nuclei as well as the microphysical processes like nucleation, condensation/evaporation and sedimentation of ice particles.

Our research is focused on the following topics such as laboratory studies of heterogeneous nucleation of different type of atmospheric ice nuclei using the differential scanning calorimetry, radiosonde measurements of cirrus clouds and relative humidity, lidar measurements on cirrus clouds, microphysical and process modelling using the box and column model (Zurich Optical and Microphysical Model).
 

• Ice nucleation measurements using emulsion and single droplet calorimetry
• Microfluidics to understand ice cloud formation
  
• Modeling of homogeneous ice nucleation from supercooled liquid droplets
• Balloon soundings
• Remote sensing of cirrus cloud (LIDAR) and analysis
• Zurich Optical and Microphysical Model (ZOMM)