The formation of ice in maritime cumuli: Insights from new observations and modeling
Abstract
Despite much advancement in the field of cloud microphysics, the measurement and observation of small ice particles has proven difficult and the exact mechanisms behind ice nucleation remain a fundamental uncertainty. This is particularly true in maritime cumulus clouds where large ice concentrations have been observed at temperatures as warm as -5°C. The work presented here provides new insight into the early formation of ice in maritime cumulus clouds through the analysis of recent observations of small ice particles, with a particular focus on an instrument capable of detecting the habit of very small ice particles, and comparison with a high resolution 3D numerical cloud model capable of representing 10 individual ice hydrometeor species, including a variety of small ice particle habits. The findings of this comparison suggest that a small ice population, formed though deposition and condensation-freezing nucleation, could be the first ice to form in maritime cumulus clouds. These small ice particles may also be responsible for nucleating the graupel and/or large frozen raindrops previously thought to be the first ice particles to form through immersion freezing. The model also suggests that contrary to the conclusions of some past observational studies, rime splintering may not be necessary to explain the early stages of ice formation at temperatures warmer than -10°C.
Degree
Ph.D.
Advisors
Lasher-Trapp, Purdue University.
Subject Area
Climate Change|Atmospheric sciences
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