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Open AccessArticle

Fog Droplet Size Distribution and the Interaction between Fog Droplets and Fine Particles during Dense Fog in Tianjin, China

by Qing Liu 1,2,3, Bingui Wu 2,4,*, Zhaoyu Wang 1 and Tianyi Hao 2,4
1
Tianjin Weather Modification Office, Tianjin 300074, China
2
Tianjin Key laboratory of Marine Meteorology, Tianjin 300074, China
3
Key Laboratory for Cloud Physics of China Meteorological Administration, Beijing 100081, China
4
Tianjin Meteorology Bureau, Tianjin 300074, China
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(3), 258; https://doi.org/10.3390/atmos11030258
Received: 6 January 2020 / Revised: 29 February 2020 / Accepted: 2 March 2020 / Published: 5 March 2020
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
From November 2016 to January 2017, there were large-scale dense fog processes in Tianjin area on the west coast of Bohai Bay, China, even strong dense fog with visibility less than 50 m occurred. Based on the observation data of fog droplet spectrum monitor, visibility sensor, environmental particle monitoring equipment and meteorological automatic station, the characteristics of fog droplet size distribution and the interaction between the fog droplets and fine particles during dense fog events were analyzed. The results show following characteristics: (1) The average concentration of fog droplets (Na), the average liquid water content (La) and the maximum liquid water content (Lmax) in the strong dense fog process are larger than those in the dense fog. The average spectrum of fog droplet size distribution conforms to Junge distribution, and they are all broad-spectrum fog with a spectrum width of about 45 μm. The average spectrum is similar to the dense fog of heavily industrialized inland in the world. (2) The maximum of fog droplet diameter during the formation stage have a good indication for the outbreak of strong dense fog. (3) The mass concentration of PM2.5 (CPM2.5) is ranged from 121–375 μg/m3, and the interaction between fog droplets and fine particles is analyzed. During the formation, development and maturity stages, fog process can scavenge atmospheric fine particles, and the scavenging efficiency of PM2.5 is more remarkable than PM10. When CPM2.5 does not exceed 350 μg/m3, the increase in the concentration of fine particles is conducive to the rapid growth of fog droplets and the sharp drop of visibility. However, when CPM2.5 exceeds the critical value, the increase has a negative feedback effect on the development of the fog process. More investigations and cases are necessary to fully assess the mechanisms related to the dense fog events in Tianjin area and further analysis will be done. View Full-Text
Keywords: fog droplet size distribution; fog; atmospheric fine particles; liquid water content; PM2.5; fog droplet spectrum fog droplet size distribution; fog; atmospheric fine particles; liquid water content; PM2.5; fog droplet spectrum
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Liu, Q.; Wu, B.; Wang, Z.; Hao, T. Fog Droplet Size Distribution and the Interaction between Fog Droplets and Fine Particles during Dense Fog in Tianjin, China. Atmosphere 2020, 11, 258.

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