10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Traces of Ice Nucleation Modes in Arctic Mixed-phase Clouds Simulated by a Habit Prediction Scheme

TEMPEI HASHINO, Gijs de Boer, Hajime Okamoto, Greg Tripoli, Kyushu University

     Abstract Number: 1133
     Working Group: Unraveling the Many Facets of Ice Nucleating Particles and Their Interactions with Clouds

Abstract
Ubiquitous and long-lasting Arctic low-level clouds are known to affect the surface energy budget through radiation especially when liquid particles are present (Curry and Ebert 1990, Hashino et al. 2016, Shupe et al. 2011). However, simulation of the mixed-phase status have been challenging partly due to their large sensitivity on ice number concentration (e.g., Morrison et al. 2011, Young et al. 2017). The ice nucleation modes active in the clouds are still open to question (e.g., Fridlind et al. 2007, Paukert and Hoose 2014). In this presentation, we make contrasts of results obtained with three ice nucleation schemes through 3D LES experiments.

A habit-prediction scheme called SHIPS (Hashino and Tripoli 2007, 2008, 2011ab) was implemented in a scalable non-hydrostatic model, UW-NMS (Tripoli and Smith 2014ab). Three ice nucleation schemes are considered: Meyers deposition-condensation freezing, Bigg-type time-dependent immersion freezing parameterization (Bigg), classical nucleation theory based scheme (CNT). For May 7th case during SHEBA campaign, it was found that large cloud droplets in downdraft freeze actively with Bigg. On the other hand, CNT immersion scheme produces much of ice over updraft where supersaturation is relatively high. This means that the initial size of frozen particles is different among the immersion schemes. Through non-linear feedback built in the habit prediction scheme, the resulting aspect ratios of plates clearly differ each other. As a result, radar reflectivity simulated with Bigg scheme better match with ground radar observation although the ice water paths of the two are similar. In the presentation, we will discuss implication of the volume dependence of freezing and formation of the large cloud droplets.