Chapter 7. Secondary Ice Production - current state of the science and recommendations for the future

TLDR

Measured ice crystal concentrations in natural clouds at modest supercooling are orders of magnitude higher than primary ice nucleating particles, implying a secondary ice production process that is crucial for cloud evolution but remains poorly understood. An international workshop convened in November 2015 to review the current state of secondary ice production science and outline future research to better constrain and improve understanding. The workshop presented examples and recommendations for in situ observations, remote sensing, laboratory investigations, and modeling approaches to advance knowledge of secondary ice production.

Abstract

Measured ice crystal concentrations in natural clouds at modest supercooling (temperature ~>−10°C) are often orders of magnitude greater than the number concentration of primary ice nucleating particles. Therefore, it has long been proposed that a secondary ice production process must exist that is able to rapidly enhance the number concentration of the ice population following initial primary ice nucleation events. Secondary ice production is important for the prediction of ice crystal concentration and the subsequent evolution of some types of clouds, but the physical basis of the process is not understood and the production rates are not well constrained. In November 2015 an international workshop was held to discuss the current state of the science and future work to constrain and improve our understanding of secondary ice production processes. Examples and recommendations for in situ observations, remote sensing, laboratory investigations, and modeling approaches are presented.