Ice‐Nucleating Particle Concentrations and Sources in Rainwater Over the Third Pole, Tibetan Plateau

Abstract

AbstractThe ice‐nucleating particles (INPs) modulate the microphysics and radiative properties of clouds. However, less is known concerning their abundance and sources in the most pristine and climatic sensitive regions, such as the Tibetan Plateau (TP). Here, to our best knowledge, we conduct the first investigation on INPs in rainwater collected in the TP region under mixed‐phase cloud conditions. The value of INP concentrations varies from 0.002 to 0.675 L−1 air over the temperature range from −7.1 to −27.5°C. This is within the INP spectra derived from precipitation under worldwide geophysical conditions and is also comparable with INP concentrations in the Arctic regions. The heat‐sensitive INPs account for 57% ± 30% of the observed INPs at −20°C and become increasingly important at higher temperatures, indicating biological particles as major contributors to INPs at temperatures above −20°C over the TP, especially on the day with additional input of biogenic materials carried by dust particles. Chemical analysis demonstrates that the rainwater components are mixture of dust particles, marine aerosol, and anthropogenic pollutants. Combined with the backward trajectory analysis, we show that dust particles transported from the surrounding deserts and originated from ground surface of TP may contribute to the heat‐resistant INPs at temperatures below −20°C.