The evolution of cloud and aerosol microphysics at the summit of Mt. Tai, China
<p>The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and the behaviours of clouds and their influence on climate. In an attempt to better understand the microphysical properties of cloud droplets, the simultaneous vari...
| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/13735/2020/acp-20-13735-2020.pdf |
| Summary: | <p>The influence of aerosols, both natural and
anthropogenic, remains a major area of uncertainty when predicting the
properties and the behaviours of clouds and their influence on climate. In
an attempt to better understand the microphysical properties of cloud
droplets, the simultaneous variations in aerosol microphysics and their
potential interactions during cloud life cycles in the North China Plain, an
intensive observation took place from 17 June to 30 July 2018 at the
summit of Mt. Tai. Cloud microphysical parameters were monitored
simultaneously with number concentrations of cloud condensation nuclei
(<span class="inline-formula"><i>N</i><sub>CCN</sub></span>) at different supersaturations, PM<span class="inline-formula"><sub>2.5</sub></span> mass concentrations,
particle size distributions and meteorological parameters. Number
concentrations of cloud droplets (<span class="inline-formula"><i>N</i><sub>C</sub></span>), liquid water content (LWC) and
effective radius of cloud droplets (<span class="inline-formula"><i>r</i><sub>eff</sub></span>) show large variations among 40
cloud events observed during the campaign. The low values of <span class="inline-formula"><i>r</i><sub>eff</sub></span> and
LWC observed at Mt. Tai are comparable with urban fog. Clouds on clean days
are more susceptible to the change in concentrations of particle number
(<span class="inline-formula"><i>N</i><sub>P</sub></span>), while clouds formed on polluted days might be more sensitive to
meteorological parameters, such as updraft velocity and cloud base height.
Through studying the size distributions of aerosol particles and cloud
droplets, we find that particles larger than 150 nm play important roles in
forming cloud droplets with the size of 5–10 <span class="inline-formula">µ</span>m. In general, LWC
consistently varies with <span class="inline-formula"><i>r</i><sub>eff</sub></span>. As <span class="inline-formula"><i>N</i><sub>C</sub></span> increases, <span class="inline-formula"><i>r</i><sub>eff</sub></span> changes
from a trimodal distribution to a unimodal distribution and shifts to
smaller size mode. By assuming a constant cloud thickness and ignoring any
lifetime effects, increase in <span class="inline-formula"><i>N</i><sub>C</sub></span> and decrease in <span class="inline-formula"><i>r</i><sub>eff</sub></span> would increase
cloud albedo, which may induce a cooling effect on the local climate system.
Our results contribute valuable information to enhance the understanding of
cloud and aerosol properties, along with their potential interactions on the
North China plain.</p> |
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| ISSN: | 1680-7316 1680-7324 |