Ice-Nucleating Particle Concentrations and Sources in Rainwater over the
Third Pole, Tibetan Plateau
Abstract
The 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 INP concentrations
vary from 0.002 to 0.675 L-1 Air over the temperature range from -7.1 to
-27.5 °C, being within the INP spectra derived from precipitation under
worldwide geophysical conditions, and are also comparable to those in
the Arctic region. The heating-sensitive INPs account for 57%±30% of
the observed INPs at -20 °C, and become increasingly important at warmer
temperature regime, indicating biogenic particles as major contributors
to INPs above -20 °C over the TP, especially, on the day with additional
input of biogenic materials carried by dust particles. Chemical analysis
demonstrates the rainwater components are mixture of dust particles,
marine aerosol, and anthropogenic pollutants. Dust particles transported
from the surrounding deserts and originated from ground surface of TP
may contribute to the heating-resistant INPs at temperatures below -20
°C.