Cloud Physics

  • Lecturer:
  • PD Dr. Ulrike Wacker

Lecture content:

Atmospheric clouds consist of drops and ice particles. These particles grow by
condensation, deposition, coagulation etc., sediment under the impact of gravity and
reach, if they do not evaporate underneath the cloud, the surface as precipitation.
Clouds are of great importance for weather and climate. They reflect incoming
sunlight back into space but also trap thermal radiation emitted by the Earth’s surface
below them by reflecting it back downwards. They are required for formation of
precipitation and also important for cleaning the atmosphere from trace gases and

This course deals with the physical processes in clouds and their mathematical
description. The lecture starts with a short introduction to the thermodynamics of the
moist atmosphere. Emphasis is then placed on the microstructure of clouds and
precipitation and its mathematical description, the evolution of drops and ice particles
and their size distribution caused by nucleation, condensation, deposition,
coagulation, riming, melting, and sedimentation are discussed. Also gas and particle
scavenging are addressed. Finally, concepts for treating clouds in complex numerical
prediction models will be explained.

It is expected that participants have basic knowledge in atmospheric science
according to the courses Atmospheric Physics and Dynamics I.

Suggested reading:

• R.R. Rogers and M.K. Yau, 1989: ‘A Short Course in Cloud Physics’, Pergamon
• D. Lamb and J. Verlinde, 2011: ‘Physics and Chemistry of Clouds’, Cambridge
University Press.
• J.M. Wallace and P.V. Hobbs, 2006: ‘Atmospheric Science’, Academic Press.
• H.R. Pruppacher and J.D. Klett, 1978: ‘Microphysics of Clouds and Precipitation’,
Kluwer Academic Publishers.