Summary of a 4-Year Fog Field Study in Northern Nanjing, Part 2: Fog Microphysics

Niu, Shengjie; Liu, D. Y.; Zhao, Lilong; Lu, Chen; Lü, Jingjing; Yang, Jing

doi:10.1007/s00024-011-0344-9

Cited by 35 publications

(18 citation statements)

References 46 publications

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“…In terms of the spectral width characteristics of fog droplets, in the six fog processes, the spectral widths are at approximately 45 μm. It can be considered that the winter (strong) dense fog in Tianjin is a broad-spectrum fog based on suggestion of Niu et al [35].…”

Section: Measurement and Data Processingmentioning

confidence: 99%

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

Liu

Wang

et al. 2020

Atmosphere

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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.

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Section: Measurement and Data Processingmentioning

confidence: 99%

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

Liu

Wang

et al. 2020

Atmosphere

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“…Usually measurements of droplet spectra reported in the literature were performed by single particle counters such as FSSP, CDP or FM-100 over the range µm. The corresponding droplet concentrations are in the range of a tenth to several hundred cm −3 (Wendisch et al, 1998;Garcıa-Garcıa et al, 2002;Gultepe and Milbrandt, 2007a;Niu et al, 2012;Price, 2011;Liu et al, 2011;Burnet et al, 2012;Lu et al, 2013;Zhao et al, 2013). In our cases, concentration values are rather low for semi-urban conditions with only one event exceeding 150 cm −3 .…”

Section: Impact Of Ccn Concentration On Fog Microstructurementioning

confidence: 44%

“…In our cases, concentration values are rather low for semi-urban conditions with only one event exceeding 150 cm −3 . For instance, Liu et al (2011) and Niu et al (2012) reported values recorded in Pancheng (China) as high as 800 and 1000 cm −3 , respectively. However we have shown that our resulting values of critical diameter are large with a median value of 3.8 µm.…”

Section: Impact Of Ccn Concentration On Fog Microstructurementioning

confidence: 99%

Experimental study of the aerosol impact on fog microphysics

Mazoyer¹,

Burnet²,

Roberts³

et al. 2018

Preprint

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Abstract. Comprehensive field campaigns dedicated to fog life cycle observation were conducted during the winters of 2010&#8211;2013 at the SIRTA observatory in the suburb of Paris. In order to document their properties, in situ microphysical measurements collected during 23 fog events are examined here. They reveal large variability in number, concentration and size of both aerosol background before the fog onset and fog droplets according to the different cases. The objective of this paper is to evaluate the impact of aerosol particles on the fog microphysics. To derive an accurate estimation of the actual activated fog droplet number concentration Nact we determine the hygro-scopicity parameter &#954;, the dry and the wet critical diameter and the critical supersaturation for each case by using an iterative procedure based on the &#954;-K&#246;hler theory that combines cloud condensation nuclei (CCN), dry particle and droplet size distribution measurements. Resulting values of &#954;&#8201;=&#8201;0.17&#8201;&#177;&#8201;0.05 were found typical of continental aerosols. Our study reveals low values of the derived critical supersaturation with a median of 0.043&#8201;% and large values for both wet and dry activation diameters. Consequently, the corresponding Nact values are low with median concentrations of 53.5&#8201;cm&#8722;3 and 111&#8201;cm&#8722;3 within the percentile 75th. No detectable trend between the concentration of aerosol particles with diameter&#8201;>&#8201;200&#8201;nm and Nact was observed. In contrast the CCN data at 0.1&#8201;% supersaturation exhibits a strong correlation with these aerosol concentrations. We therefore conclude that the actual supersaturations reached during these fog episodes are too low and no simultaneous increase of aerosols&#8201;>&#8201;200&#8201;nm and droplet concentrations can be observed. Moreover our analysis suggests that a high aerosol loading limits the supersaturation values. It is also found that the activated fraction mainly depends on the aerosol size while the hygroscopicity appears to be of a secondary importance. Although radiative fogs are usually associated with higher aerosol loading rather than to stratus lowering events, our analysis reveals that the activated particle concentrations at the beginning of the event are similar for both types of fog. However the evolution of the droplet concentration during the fog life cycle shows significant differences between both types of fog.

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“…In our cases, concentration values are rather low for semi-urban conditions with only one event exceeding 150 cm −3 . For instance, Liu et al (2011) andNiu et al (2012) reported values 20 recorded in Pancheng (China) as high as 800 and 1000 cm −3 , respectively. However we have shown that our resulting values of critical diameter are large with a median value of 3.8 µm.…”

Section: Discussionmentioning

confidence: 99%

“…Usually measure-15 ments of droplet spectra reported in the literature were performed by single particle counters such as FSSP, CDP or FM-100 over the range µm. The corresponding droplet concentrations are in the range of a tenth to several hundred cm −3 (Wendisch et al, 1998;Garcıa-Garcıa et al, 2002;Gultepe and Milbrandt, 2007a;Niu et al, 2012;Price, 2011;Liu et al, 2011;Burnet et al, 2012;Lu et al, 2013;Zhao et al, 2013). In our cases, concentration values are rather low for semi-urban conditions with only one event exceeding 150 cm −3 .…”

Section: Discussionmentioning

confidence: 99%

Experimental study of the aerosol impact on fog microphysics

Mazoyer

Burnet

Roberts

et al. 2016

Preprint

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Abstract.Comprehensive field campaigns dedicated to fog life cycle observation were conducted during the winters of [2010][2011][2012][2013] at the SIRTA observatory in the suburb of Paris. In order to document their properties, in situ microphysical measurements collected during 23 fog events are examined here. They reveal large variability in number, concentration and size of both aerosol background before the fog onset and fog droplets according to the different cases. The objective of this paper is to 5 evaluate the impact of aerosol particles on the fog microphysics.To derive an accurate estimation of the actual activated fog droplet number concentration N act, we determine the hygroscopicity parameter κ, the dry and the wet critical diameter and the critical supersaturation for each case by using an iterative procedure based on the κ-Köhler theory that combines cloud condensation nuclei (CCN), dry particle and droplet size distribution measurements. Resulting values of κ = 0.17 ± 0.05 were found typical of continental aerosols. Our study reveals No detectable trend between the concentration of aerosol particles with diameter > 200 nm and N act was observed. In contrast the CCN data at 0.1 % supersaturation exhibits a strong correlation with these aerosol concentrations. We therefore 15 conclude that the actual supersaturations reached during these fog episodes are too low and no simultaneous increase of aerosols > 200 nm and droplet concentrations can be observed. Moreover our analysis suggests that a high aerosol loading limits the supersaturation values. It is also found that the activated fraction mainly depends on the aerosol size while the hygroscopicity appears to be of a secondary importance.Although radiative fogs are usually associated with higher aerosol loading rather than to stratus lowering events, our analysis 20 reveals that the activated particle concentrations at the beginning of the event are similar for both types of fog. However the evolution of the droplet concentration during the fog life cycle shows significant differences between both types of fog.

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Summary of a 4-Year Fog Field Study in Northern Nanjing, Part 2: Fog Microphysics

Cited by 35 publications

References 46 publications

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

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

Experimental study of the aerosol impact on fog microphysics

Experimental study of the aerosol impact on fog microphysics

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