Lab and field studies of the ability of aerosols to act as ice nuclei (IN)

The importance of ice crystals in clouds for our climate is manifold: Their presence, number and shape influences the optical properties of clouds, the formation of precipitation and their lifetime. All of these aspects have an impact on the radiation balance and therefore on climate.

In our ice nucleation lab, we are focussing on the first step in this chain, the formation or nucleation of ice and the influencing factors which are: The number, size, and chemical composition of aerosol particles which act as „catalysts“ for the formation of ice and the environmental conditions like temperature and relative humidity.

One aspect is further complicating the study of ice nucleation and its consequences for
clouds: The fact that there are several modes or mechanisms, by which ice can form:

One of the goals of our work is to study all of these nucleation/freezing modes experimentally to learn more about their relative importance in real world clouds. To achieve this, we have developed several instruments to study these processes individually:

• The Zurich Ice Nucleation Chamber ZINC (focus on deposition and condensation freezing)

• The Immersion Mode Cooling Chamber IMCA (an extension for the ZINC instrument)

• The COLLISION Chamber (to study contact freezing)

• The Portable Ice Nucleation Chamber PINC (a portable version of ZINC for field studies)