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Review of experimental studies of secondary ice production

Abstract. Secondary ice production (SIP) plays a key role in the formation of ice
particles in tropospheric clouds. Future improvement of the accuracy of
weather prediction and climate models relies on a proper description of SIP
in numerical simulations. For now, laboratory studies remain a primary tool
for developing physically based parameterizations for cloud modeling. Over
the past 7 decades, six different SIP-identifying mechanisms have
emerged: (1) shattering during droplet freezing, (2) the rime-splintering
(Hallett–Mossop) process, (3) fragmentation due to ice–ice collision, (4) ice particle fragmentation due to thermal shock, (5) fragmentation of
sublimating ice, and (6) activation of ice-nucleating particles in transient
supersaturation around freezing drops. This work presents a critical review
of the laboratory studies related to secondary ice production. While some of
the six mechanisms have received little research attention, for others
contradictory results have been obtained by different research groups.
Unfortunately, despite vast investigative efforts, the lack of consistency
and the gaps in the accumulated knowledge hinder the development of
quantitative descriptions of any of the six SIP mechanisms. The present work
aims to identify gaps in our knowledge of SIP as well as to stimulate
further laboratory studies focused on obtaining a quantitative description
of efficiencies for each SIP mechanism.