A~comprehensive parameterization of heterogeneous ice nucleation of dust surrogate: laboratory study with hematite particles and its application to atmospheric models

N. Hiranuma, M. Paukert, I. Steinke, K. Zhang, G. Kulkarni, C. Hoose, M. Schnaiter, H. Saathoff, O. Möhler
2014 Atmospheric Chemistry and Physics Discussions  
A new heterogeneous ice nucleation parameterization that covers a~wide temperature range (−36 to −78 °C) is presented. Developing and testing such an ice nucleation parameterization, which is constrained through identical experimental conditions, is critical in order to accurately simulate the ice nucleation processes in cirrus clouds. The surface-scaled ice nucleation efficiencies of hematite particles, inferred by <i>n</i><sub>s</sub>, were derived from AIDA (Aerosol Interaction and Dynamics
more » ... n the Atmosphere) cloud chamber measurements under water subsaturated conditions that were realized by continuously changing temperature (<i>T</i>) and relative humidity with respect to ice (RH<sub>ice</sub>) in the chamber. Our measurements showed several different pathways to nucleate ice depending on T and RH<sub>ice</sub> conditions. For instance, almost <i>T</i>-independent freezing was observed at −60 °C < <i>T</i> < &minus;50 °C, where RH<sub>ice</sub> explicitly controlled ice nucleation efficiency, while both <i>T</i> and RH<sub>ice</sub> played roles in other two <i>T</i> regimes: −78 °C < <i>T</i> < &minus;60 °C and −50 °C < <i>T</i> < &minus;36 °C. More specifically, observations at <i>T</i> colder than −60 °C revealed that higher RH<sub>ice</sub> was necessary to maintain constant <i>n</i><sub>s</sub>, whereas <i>T</i> may have played a significant role in ice nucleation at <i>T</i> warmer than −50 °C. We implemented new <i>n</i><sub>s</sub> parameterizations into two cloud models to investigate its sensitivity and compare with the existing ice nucleation schemes towards simulating cirrus cloud properties. Our results show that the new AIDA-based parameterizations lead to an order of magnitude higher ice crystal concentrations and inhibition of homogeneous nucleation in colder temperature regions. Our cloud simulation results suggest that atmospheric dust particles that form ice nuclei at lower temperatures, below −36 °C, can potentially have stronger influence on cloud properties such as cloud longevity and initiation when compared to previous parameterizations.
doi:10.5194/acpd-14-16493-2014 fatcat:xc466cb4dzb2fcwmzf5d37wgmi