Ice Nucleation in Clouds

Abstract

The formation of ice in clouds is very important to the precipitation development in the cold and mixed-phase clouds and also for the radiative budget of clouds. Understanding the process of ice nucleation and predicting the ice concentration posses a major challenge. This challenge arises due to the fact that there are large gaps in our understanding of the ice nucleation and ice multiplication processes occurring inside natural clouds. Although the observations of ice nuclei in the atmosphere began about 70 years ago, globally the measurements are very sparse. The quantification of the types of ice nuclei in the atmosphere is also not to the desired levels. The ice nucleation at warmer temperatures by the ice nuclei present in the atmosphere is not well understood. This comes from the fact that there are several orders of magnitude difference between the observed concentration of ice nuclei in the atmosphere and the ice particle concentration in clouds. Whether the proposed mechanisms of secondary ice multiplication processes can explain this discrepancy is still not proven. There are several gaps that need to be addressed to quantify correctly the ice formation in clouds.