Abstract
Ice-nucleating particles (INPs) play a key role in ice formation and
cloud microphysics and thus significantly impact the water cycle and the
climate. However, our understanding of atmospheric INPs, particularly
their sources, emissions, and spatiotemporal variability, is incomplete.
While the enhancement of atmospheric INP concentrations with rainfall
has been previously shown, a mechanistic understanding of the process is
lacking. Here, we link detailed precipitation observations with
near-surface atmospheric INP concentrations at a semi-arid grassland
site in Colorado. Considering the during-precipitation air samples, INP
concentrations positively correlate with cumulative rainfall kinetic
energy and amount, suggesting that INP aerosolization is induced by
raindrop and hailstone impact. By additionally analyzing the INP content
of precipitation water, terrestrial source samples, and heat-treated
samples, we demonstrate that local plants are the most important source
of precipitation-induced INPs. Should INPs aerosolized by precipitation
rise to cloud height, they could influence cloud ice fraction and
initiate precipitation resulting in an aerosol-cloud-precipitation
feedback.