Mechanisms for the Ice Nucleus Aerosols and their Indirect Effects: Cloud Modelling

The present thesis work highlights the importance of various secondary ice production mechanisms, ice nucleating activity of various biological particles and the time dependence of INP freezing in nucleating overall ice. Also the effect of increasing anthropogenic solid aerosol loading on cloud microphysical and radiative properties are discussed. This study found that age of the cloud is crucial for relative activity of various secondary ice production processes.

A significant amount of global precipitation is linked to the formation
of ice particles in clouds. In addition, ice microphysical processes affect
the Earth’s radiation budget. The presence of ice in clouds is a culmination
of many complex processes that are still poorly understood.
The role of clouds containing ice on global radiation and hydrological
budgets is highly uncertain.
In this thesis, the author examines the importance of various ice
microphysical processes in mixed-phase clouds using numerical model
simulations. It is found that the ice nucleation activity of various
biological particles, as well as the time-dependent freezing of ice
nucleating particles (INPs), have a minimal effect on the properties of
mixed-phase clouds. For the first time, the relative importance of four
secondary ice production mechanisms is investigated in various cloud
types. Moreover, the thesis investigates how an increase in aerosols
through anthropogenic activities leads to changes in cloud radiative
properties. Also, this study newly discovered two new indirect effects
arising from SIP and from time dependence of INP freezing.