Characteristics and Distribution of efficient ice nucleating particles in rainwater and soil

Abstract

Ice nucleating particles (INPs) might influence precipitation and are related to the hydrologic cycle by initiating ice formation. The contribution of efficient INPs (and almost all biological particles) is significant in catalyzing the freezing of ice at relatively warm temperatures (> −10 °C). However, to what extent biological matter functions as INPs in clouds is poorly understood and the large gap in investigating the properties of ice nucleating ability in rainwater and variation in INPs during a single precipitation event needs to be addressed. In this study, we tested the ice nucleating activity in rainwater and soil to probe the characteristics and distribution of INPs and tried to trace the possible sources of INPs. We suggested that the biological INPs dubbed efficient INPs are commonly present in rainwater and soil at > −10 °C, and it is surprising that unknown efficient INPs, probably derived from microbes, were shown to dominate at warmer temperatures by detection of the potential known ice nucleating active genera through high-throughput sequencing analysis. Furthermore, certain heat-resistant efficient INPs were found in rainwater and a few nanoscale efficient biological INPs were retained partially in soil. Moreover, we also found that nonlocally sourced inefficient INPs dominated in precipitation induction and efficient INPs became gradually more involved as precipitation proceeded by comparing the diverse periods of one entire heavy rainfall event.