image: Photos of the fog-water collection site (a) and the fog-microphysics observation site (b) in the XSBN-FOG-2019 experiment. view more
Credit: ©Science China Press
This study is led by Prof. Shengjie Niu and Prof. Chunsong Lu of the Nanjing University of Information Science & Technology. The research team cooperated with the team of Prof. Qinghai Song from the Key Laboratory of Tropical Forest Ecology of the Chinese Academy of Sciences, and conducted a three-month field experiment focusing on the physical and chemical characteristics of fog in a tropical rainforest in Xishuangbanna, Southwest China, in the foggy season of 2019.
The radiation fog that occurs frequently during the foggy season of the tropical rainforest is an important source of water vapor in the forest system. Based on the results of this experiment, the researchers explored the formation and dissipation mechanisms and physical and chemical characteristics of radiation fog in this area, deepening the knowledge and understanding of radiation fog in the tropical rainforest.
The fog formed at midnight and persisted because of the increased long-wave radiative cooling combined with the high relative humidity, gentle breeze, and a relatively low aerosol number concentration in the forest; the fog dissipated before noon due to the increasing turbulence near the surface. This diurnal cycle is typical for radiation fog.
The microphysical fog properties included relatively low fog droplet number concentrations, large droplet sizes, high liquid water content, narrow droplet number-size distributions, and high supersaturation. The chemical properties showed that the fog water was slightly alkaline with low electrical conductivity, whereas the highest proportions of anions and cations therein were Cl- and Ca2+, respectively; the chemical components were enriched in small fog droplets.
In addition, the researchers indirectly calculated the fog supersaturation according to the Köhler theory. They found that condensation broadens the droplet number-size distribution at relatively low supersaturation, which is positively correlated with the fog-droplet number concentration and negatively correlated with the droplet mean-volume diameter.
See the article:
https://www.sciengine.com/publisher/scp/journal/SCES/64/11/10.1007/s11430-020-9766-4?slug=fulltext
https://link.springer.com/article/10.1007/s11430-020-9766-4
Journal
Science China Earth Sciences