Optical Modeling of Sea Salt Aerosols Using in situ Measured Size Distributions and the Impact of Larger Size Particles

Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation.The size distribution of these particles is crucial in determining their bulk optical properties.In this study,we analyzed in situ measured size distributions of sea salt aerosols from four field campaigns and used multi-mode lognormal size distributions to fit the data.We employed super-spheroids and coated super-spheroids to account for the particles’non-sphericity,inhomogeneity,and hysteresis effect during the deliquescence and crystallization processes.To compute the singlescattering properties of sea salt aerosols,we used the state-of-the-art invariant imbedding T-matrix method,which allows us to obtain accurate optical properties for sea salt aerosols with a maximum volume-equivalent diameter of 12μm at a wavelength of 532 nm.Our results demonstrated that the particle models developed in this study were successful in replicating both the measured depolarization and lidar ratios at various relative humidity(RH)levels.Importantly,we observed that large-size particles with diameters larger than 4μm had a substantial impact on the optical properties of sea salt aerosols,which has not been accounted for in previous studies.Specifically,excluding particles with diameters larger than 4μm led to underestimating the scattering and backscattering coefficients by 27%−38%and 43%−60%,respectively,for the ACE-Asia field campaign.Additionally,the depolarization ratios were underestimated by 0.15 within the 50%−70%RH range.These findings emphasize the necessity of considering large particle sizes for optical modeling of sea salt aerosols.

Simultaneous estimation of aerosol optical constants and size distribution from angular light-scattering measurement signals

The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.

Preliminary study on concentrations and size distribution of marine aerosols over the East China Sea

In summer and winter, 1987,and in spring and autumn, 1988, the concentrations and size distribution of marine aerosols were measured over the East China Sea and the South Japan Sea. This paper deals with the study on the seasonal variation of the marine aerosols with the meteorological parameters, the differences and the relations between the marine and continental aerosols. The results show that the marine aerosol concentrations and size distribution over the East China Sea have distinct seasonal change characteristics, which may be attributed to the East Asian atmospheric circulation. The size distribution is discussed by using a three-parameter size distribution model.

Airborne Observations of Cloud Condensation Nuclei Spectra and Aerosols over East Inner Mongolia

A set of vertical profiles of aerosol number concentrations, size distributions and cloud condensation nuclei（CCN）spectra was observed using a passive cloud and aerosol spectrometer（PCASP） and cloud condensation nuclei counter, over the Tongliao area, East Inner Mongolia, China. The results showed that the average aerosol number concentration in this region was much lower than that in heavily polluted areas. Monthly average aerosol number concentrations within the boundary layer reached a maximum in May and a minimum in September, and the variations in CCN number concentrations at different supersaturations showed the same trend. The parameters c and k of the empirical function N = c S^kwere 539 and1.477 under clean conditions, and their counterparts under polluted conditions were 1615 and 1.42. Measurements from the airborne probe mounted on a Yun-12（Y12） aircraft, together with Hybrid Single-Particle Lagrangian Integrated Trajectory model backward trajectories indicated that the air mass from the south of Tongliao contained a high concentration of aerosol particles（1000–2500 cm^（-3）） in the middle and lower parts of the troposphere. Moreover, detailed intercomparison of data obtained on two days in 2010 indicated that the activation efficiency in terms of the ratio of NCCNto N_a（aerosols measured from PCASP） was 0.74（0.4 supersaturations） when the air mass mainly came from south of Tongliao, and this value increased to 0.83 on the relatively cleaner day. Thus, long-range transport of anthropogenic pollutants from heavily polluted mega cities,such as Beijing and Tianjin, may result in slightly decreasing activation efficiencies.

MEASUREMENTS OF PARTICLE NUMBER SIZE DISTRIBUTIONS AND NEW PARTICLE FORMATION EVENTS DURING WINTER IN THE PEARL RIVER DELTA REGION,CHINA

Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode(20-100 nm),accumulation mode(100 nm-1μm) and coarse mode(1-20 μm) particles were 1 552,7 470,4 012,and 19 cm-3,respectively.The volume concentration of accumulation mode particles with peak at 300 nm accounted for over 70% of the total volume concentration.Diurnal variations and dependencies on meteorological parameters of PNSD were investigated.The diurnal variation of nucleation mode particles was mainly influenced by new particle formation events,while the diurnal variation of Aitken mode particles correlated to the traffic emission and the growth process of nucleation mode particles.When the PRD region was controlled by a cold high pressure,conditions of low relative humidity,high wind speed and strong radiation are favorable for the occurrence of new particle formation(NPF) events.The frequency of occurrence of NPF events was 21.3% during the whole measurement period.Parameters describing NPF events,including growth rate(GR) and source rate of condensable vapor(Q),were slightly larger than those in previous literature.This suggests that intense photochemical and biological activities may be the source of condensable vapor for particle growth,even during winter in the PRD.

A Comparison of Two Bulk Microphysics Parameterizations for the Study of Aerosol Impacts on an Idealized Supercell

Idealized supercell storms are simulated with two aerosol-aware bulk microphysics schemes(BMSs),the Thompson and the Chen-Liu-Reisner(CLR),using the Weather Research and Forecast(WRF)model.The objective of this study is to investigate the parameterizations of aerosol effects on cloud and precipitation characteristics and assess the necessity of introducing aerosols into a weather prediction model at fine grid resolution.The results show that aerosols play a decisive role in the composition of clouds in terms of the mixing ratios and number concentrations of liquid and ice hydrometeors in an intense supercell storm.The storm consists of a large amount of cloud water and snow in the polluted environment,but a large amount of rainwater and graupel instead in the clean environment.The total precipitation and rain intensity are suppressed in the CLR scheme more than in the Thompson scheme in the first three hours of storm simulations.The critical processes explaining the differences are the auto-conversion rate in the warm-rain process at the beginning of storm intensification and the low-level cooling induced by large ice hydrometeors.The cloud condensation nuclei(CCN)activation and auto-conversion processes of the two schemes exhibit considerable differences,indicating the inherent uncertainty of the parameterized aerosol effects among different BMSs.Beyond the aerosol effects,the fall speed characteristics of graupel in the two schemes play an important role in the storm dynamics and precipitation via low-level cooling.The rapid intensification of storms simulated with the Thompson scheme is attributed to the production of hail-like graupel.

Polarimetric Study of the Fine Aerosol Fraction in Beijing

Measurements of aerosol optical characteris- tics were carried out with a Photoelectric Aerosol Nephelometer （PhAN） in Beijing and at Xinglong Obser- vatory, which is located 150 km northeast of Beijing. Aerosol size distributions were retrieved by means of the inverse problem solution. Mean volume size distributions of the fine aerosol fraction were unimodal with the maximum radius in the range 0.11-0.15 pm. Accumula- tion of aerosol matter in the air basin of Beijing takes place mainly due to the growth of particle size, but not their number. A simple optical method to detect aerosol nonsphericity is proposed.

Observed Changes in Aerosol Physical and Optical Properties before and after Precipitation Events

Precipitation scavenging of aerosol particles is an important removal process in the atmosphere that can change aerosol physical and optical properties. This paper analyzes the changes in aerosol physical and optical properties before and after four rain events using in situ observations of mass concentration, number concentration, particle size distribution, scattering and absorption coefficients of aerosols in June and July 2013 at the Xianghe comprehensive atmospheric observation station in China. The results show the effect of rain scavenging is related to the rain intensity and duration, the wind speed and direction. During the rain events, the temporal variation of aerosol number concentration was consistent with the variation in mass concentration, but their size-resolved scavenging ratios were different. After the rain events, the increase in aerosol mass concentration began with an increase in particles with diameter ＆lt;0.8 μm [measured using an aerodynamic particle sizer（APS）], and fine particles with diameter ＆lt;0.1 μm [measured using a scanning mobility particle sizer（SMPS）]. Rainfall was most efficient at removing particles with diameter ～0.6 μm and greater than 3.5 μm. The changes in peak values of the particle number distribution（measured using the SMPS） before and after the rain events reflect the strong scavenging effect on particles within the 100–120 nm size range. The variation patterns of aerosol scattering and absorption coefficients before and after the rain events were similar, but their scavenging ratios differed, which may have been related to the aerosol particle size distribution and chemical composition.

Accurate Shortwave Radiation Simulation with a Two-Layer Aerosol Model in Xinjiang Region

To harness the rich solar energy resources in Xinjiang Region of Northwest China,this study tries to address the issue of lack of downward surface shortwave radiation(DSSR)observations and the need to improve the accuracy of satellite retrieval and numerical simulation of DSSR under varied sky and meteorological conditions.(1)A two-layer aerosol model specific to Xinjiang was developed to capture the vertical distributions of aerosols based on multiple data sources including lidar,GPS sounding,ground meteorological observations,and profiles from the ECMWF reanalysis version 5(ERA5)data.The results show that the ERA5/PBLH(planetary boundary layer height)and ERA5/ALH(aerosol layer height)could be used to establish the two-layer aerosol model and characterize the vertical distribution of aerosols in Xinjiang Region.(2)Using the Santa Barbara Discrete Atmospheric Radiative Transfer(SBDART)model,a localized inverse model of clear-sky DSSR was established.After parameter adjustment and using the optimal combination of input parameters for DSSR simulation together with the two-layer aerosol model,the model-simulated DSSR(DSSRSBD)under clear-sky conditions improved significantly compared to the initial results,with all fitting indices greatly improved.(3)In addition,the study demonstrated that the impact of the two-layer aerosol model on DSSR was more pronounced under dust conditions than clear-sky conditions.(4)Using the localized clear-sky DSSR inversion model and its required parameters,simulations were also conducted to capture the spatiotemporal distribution of DSSR under clear-sky conditions in Xinjiang from 2017 to 2019.The annual average DSSR_(SBD)under clear-sky conditions in Xinjiang during 2017–2019 was 606.78 W m^(-2),while DSSR from CERES(DSSR_(CER))under the same conditions was generally higher(703.95 W m^(-2)).(5)It is found that satellite remote sensing products experienced data loss in high-altitude snow areas,where numerical simulation technology could serve as a valuable complement.

Aerosol size distributions during haze episodes in winter in Jinan, China

Number concentrations and distributions of 10-10,000 nm particles in a large city （Jinan） in the North China Plain were measured in winter 2009. The mean number concentrations of nucleation mode （10-20 nm）, Aitken mode （20-100 nm）, and accumulation mode （100-1000 nm） particles, as well as total particles were 925, 6898, 2476, and 10,299cm-3, respectively. Two severe haze episodes, with elevated concentrations caused by pollutants accumulating, were observed. Accumulation mode particle concen- trations were significantly higher during the episodes than on clear days, and nucleation mode particle concentrations were pronouncedly higher on clear days than during the episodes. The peaks of domi- nant number, surface area, and mass size distributions were around 30-50, 200-300, and 200-400 rim, respectively, both during the haze episodes and on clear days, but elevated mass and surface area con- centrations around 500-600 nm were also observed during the haze episodes, suggesting these particles had significant contributions to haze formation. These particles were probably formed through larger droplets in cloud and fog evaporating. Two new particle formation events, probably triggered by strong photochemical processes on clear days and significant traffic emissions during haze episode 2, were found. Significant insights were made into haze formation in a oolluted Chinese urban area.

Spatial–temporal characteristics of haze and vertical distribution of aerosols over the Yangtze River Delta of China

Variation of haze events occurred in the Yangtze River Delta（YRD） of China, the characteristics of meteorological elements and the vertical distribution of aerosols during haze episodes were analyzed by utilizing data of ground observation, radiosonde and CALIPSO. The results illustrate that the frequency of haze events between 1981 and 2010 peaked in winter but bottomed out in summer and decreased from north to south in the YRD region, reaching at the lowest point in ＂low frequency center＂ - Shanghai. When haze happened, the most seriously affected area was 2-4 km above the ground and the concentrated range of total backscattering coefficient（TBC） that decreased with altitude was 0.8 × 10^（-3）-2.5 × 10^（-3） km^（-1）·sr^（-1）. Particulate depolarization ratio（PDR） was less than 40%in a large part and 93% aerosols over the YRD area were regular particles, while the irregular ones concentrated on 2 km above the surface and the irregularity rose up but the diversity diminished when altitude increased. Color ratio（CR） was lower than 1.2 mostly at all altitudes and distributed asymmetrically above the ground. Nearly 80% aerosols under10 km were fine particles（CR 〈1.0） clustered at 2-4 km. Large particles（CR 〉 1.2） aggregated in lower troposphere massively yet relatively smaller ones gathered in middle and upper troposphere. In the YRD region, aerosols with more powerful capabilities were wider and less regular than the ones of Northwestern China.

Origin,evolution,and distribution of atmospheric aerosol particles in Asia

In recent years, Asia became the region with the highest increase in rate of urbanization and economic development in the world. According to recent estimates from the United Nations, the world population will increase 36% between 2000 and 2030, leading to a doubling of the number of urban dwellers in less developed regions, like Asia. Such rapid economic development has many associated environmental problems, including development of heavy aerosol pollution over Asia.

Vertical Distributions of Aerosol Optical Properties during Haze and Floating Dust Weather in Shanghai

A comparative study on the vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai was conducted based on the data obtained from a micro pulse lidar.There was a distinct difference in layer thickness and extinction coefficient under the two types of weather conditions.Aerosols were concentrated below 1 km and the aerosol extinction coefficients ranged from 0.25 to 1.50km^（-1） on haze days.In contrast,aerosols with smaller extinction coefficients（0.20 0.35 km^（-1）） accumulated mainly from the surface to 2 km on floating dust days.The seasonal variations of extinction and aerosol optical depth（AOD） for both haze and floating dust cases were similar greatest in winter,smaller in spring,and smallest in autumn.More than 85%of the aerosols appeared in the atmosphere below 1 km during severe haze and floating dust weather.The diurnal variation of the extinction coefficient of haze exhibited a bimodal shape with two peaks in the morning or at noon,and at nightfall,respectively.The aerosol extinction coefficient gradually increased throughout the day during floating dust weather.Case studies showed that haze aerosols were generated from the surface and then lifted up,but floating dust aerosols were transported vertically from higher altitude to the surface.The AOD during floating dust weather was higher than that during haze.The boundary layer was more stable during haze than during floating dust weather.

Direct Radiative Effects of Dust Aerosols over Northwest China Revealed by Satellite-Derived Aerosol Three-Dimensional Distribution

Northwest China is recognized as a main source and a major transport channel of dust aerosols in East Asia.With a fragile ecological environment,this region is quite sensitive to global climate change.Based on the satellite-derived aerosol three-dimensional distribution,the direct radiative effects of dust aerosols over Northwest China are evaluated.Aerosols over Northwest China are mainly distributed in the Tarim Basin,Junggar Basin,Gobi Desert,and Loess Plateau.The aerosol extinction coefficients are greater than 0.36 km-1 over the Tarim Basin and 0.16 km^(-1) over the Gobi Desert and Loess Plateau,decreasing with height.Aerosols over Northwest China are mainly composed of pure dust and polluted dust.These dust aerosols can modify the horizontal temperature gradient,vertical thermodynamic structure,and diurnal temperature range by absorbing and scattering shortwave radiation and emitting longwave radiation.For the column atmosphere,the radiative effect of dust aerosols shows heating effect of approximately 0.3 K day^(-1) during the daytime and cooling effect of approximately-0.4 K day^(-1) at night.In the vertical direction,dust aerosols can heat up the lower atmosphere(0.5–1.5 K day^(-1))and cool down the upper atmosphere(about-1.0 K day^(-1))during the daytime,while they cool down the lower atmosphere(-3 to-1.5 K day^(-1))and heat up the upper atmosphere(1–1.5 K day^(-1))at night.There are also significant lateral and vertical variations in the dust radiative effects corresponding to their spatial distributions.This study provides some scientific basis for reducing uncertainty in the investigation of aerosol radiative effects and provides observation evidence for simulation studies.

Physicochemical and toxicological characteristics of nanoparticles in aerosols in southern Thailand during recent haze episodes in lower southeast Asia

Transboundary haze from biomass burning is one of the most important air pollutions in Southeast Asia.The most recent serious haze episode occurred in 2015.Southern Thailand was affected by the haze during September to October when the particulate matter concentration hit a record high.We investigated physical and chemical characteristics of aerosols,including concentration and aerosol size distribution down to sub-micron sizes during haze episodes in 2013 and 2015 and,for reference,an insignificant haze period in 2017.The highest total suspended particulates and PM 10 levels in Hat Yai city were 340.1 and 322.5μg/m^3.The mass fractions were nanoparticles(<100 nm)3.1%-14.8%and fine particles(<1μm)54.6%-59.1%.Polycyclic aromatic hydrocarbon size distributions in haze periods peaked at 0.75μm and the concentrations are 2-30 times higher than the normal period.High molecular weight(4-6 ring)PAHs during the haze episode contribute to about 56.7%-88.0%for nanoparticles.The average values of benzo(a)pyrene toxic equivalency quotient were 3.34±2.54ng/m^3 in the 2015 haze period but only 0.89±0.17 ng/m^3 in 2017.It is clear that particles smaller than 1μm,were highly toxic.Nanoparticles contributed 19.4%-26.0%of total BaP-TEQ,whereas the mass fraction is 13.1%-14.8%.Thus the nanoparticles were more carcinogenic and can cause greater health effect than larger particles.The fraction of BaP-TEQ for nanoparticles during 2017 non-haze period was nearly the same,while the mass fraction was lower.This indicates that nanoparticles are the significant source of carcinogenic aerosols both during haze and non-haze periods.

Characteristics of the water-soluble components of aerosol particles in Hefei,China

Size-classified daily aerosol mass concentrations and concentrations of water-soluble inorganic ions were measured in Hefei,China,in four representative months between September 2012 and August 2013.An annual average mass concentration of 169.09μg/m^3 for total suspended particulate（TSP）was measured using an Andersen Mark-II cascade impactor.The seasonal average mass concentration was highest in winter（234.73μg/m^3）and lowest in summer（91.71μg/m^3）.Water-soluble ions accounted for 59.49%,32.90%,48.62%and 37.08%of the aerosol mass concentration in winter,spring,summer,and fall,respectively,which indicated that ionic species were the primary constituents of the atmospheric aerosols.The four most abundant ions were NO3^-,SO4^2-,Ca^2＋ and NH4^＋.With the exception of Ca^2＋,the mass concentrations of water-soluble ions were in an intermediate range compared with the levels for other Chinese cities.Sulfate,nitrate,and ammonium were the dominant fine-particle species,which were bimodally distributed in spring,summer and fall;however,the size distribution became unimodal in winter,with a peak at 1.1–2.1μm.The Ca^2＋ peak occurred at approximately 4.7–5.8μm in all seasons.The cation to anion ratio was close to 1.4,which suggested that the aerosol particles were alkalescent in Hefei.The average NO3^-/SO4^2-mass ratio was 1.10 in Hefei,which indicated that mobile source emissions were predominant.Significant positive correlation coefficients between the concentrations of NH4^＋ and SO4^2-,NH4^＋ and NO3^-,SO4^2-and NO3^-,and Mg^2＋ and Ca^2＋ were also indicated,suggesting that aerosol particles may be present as（NH4）2SO4,NH4HSO4,and NH4NO3.

Comparison of aerosol characteristics during haze periods over two urban agglomerations in China using CALIPSO observations

Using CALIPSO （cloud-aerosol lidar and infrared pathfinder satellite observation） vertical observation data during haze periods from January 2007 to December 2008, we analyzed differences in aerosol char- acteristics near the surface, as well as in the middle troposphere between the Beijing-Tianjin-Hebei metropolitan region （Area A） and the Yangtze River Delta region （Area B） in China. One significant dif- ference was that haze pollution in Area A was related to local and non-local aerosols, while in Area B it was related to local anthropogenic sources. In all seasons apart from autumn, aerosol pollution in Area A was more severe than in Area B, both near the surface and at higher altitudes, In Area A, non-spherical aerosols were dominant from 0 to 4 km in spring, summer, and winter; while in autumn, there were con- siderably high numbers of non-spherical aerosols below 0.5 km, and near-spherical aerosols from 0.5 to 4 km. In Area B, both near-spherical and non-spherical aerosols were common in all seasons. Moreover, aerosols with attenuated color ratios of 0-0.2 were more common in all seasons in Area A than in Area B, indicating that fine particle pollution in Area A was more serious than in Area B. Finally, relatively large aerosols linked to gravity settling appeared more frequently near the surface in Area A than in Area B.

GROUND-BASED REMOTE SENSING OF THE SIZE DISTRIBUTION OF PINATOBU'S VOLCANIC CLOUD

In this paper,data of solar direct spectral radiance observation in summer and autumn of 1990 and 1991 were used to derive the average atmospheric extinction spectra for very clear days each year.The difference of these two extinction spectra is obvious and considered as the contribution of volcanic cloud resulting from Pinatobu's volcanic eruption in middle June of 1991.This average size distribution of volcanic cloud was retrieved from the difference spectra and given in this paper which will be useful for estimation and modeling of the effects of volcanic eruption.

Haze insights and mitigation in China: An overview

The present article provides an overview of the chemical and physical features of haze in China, focusing on the relationship between haze and atmospheric fine particles, and the formation mechanism of haze. It also summarizes several of control technologies and strategies to mitigate the occurrence of haze. The development of instruments and the analysis of measurements of ambient particles and precursor concentrations have provided important information about haze formation. Indeed, the use of new instruments has greatly facilitated current haze research in China. Examples of insightful results include the relationship between fine particles and haze, the chemical compositions and sources of particles, the impacts of the aging process on haze formation, and the application of technologies that control the formation of haze. Based on these results, two relevant issues need to be addressed： understanding the relationship between haze and fine particles and understanding how to control PM2.5.

Macro-and Micro-Structures of Heavy Fogs and Visibility in the Dayaoshan Expressway

Belonging to the southern subtropical moist type of monsoon climate, the Nanling mountainous area experiences heavy fogs whenever quasi-stationary fronts appear there from September to May. There can be as many as 15-18 days of heavy fogs per month. Fogs have more serious consequences in the Lechang-Ruyuan section of the Beijing-Zhuhai Expressway （the longest expressway in China） that passes through the main part of the Nanling Mts., where the road rises from 200 m to more than 800 m above sea level （ASL）. For a major motorway in the mountainous areas of Nanling Mts., two multidisciplinary integrated field observations were carried out, which measured visibility by the naked eyes, visibility by instrument, spectrum of fogdrops, liquid water content （LWC） of fog, tethered sounding, dual-parameter low-level sounding, turbulence diffusion within fog layers, aerosol spectra of size and composition, sampled fog water compositions, and sampled rainwater compositions. Typical cases were probed for their analyses of synoptics, micro- and macro-structures and microphysics. It is understood that heavy fogs take place with high frequency in the area and bring about serious consequences. Being typical advection and upslope fogs, they are in essence low-lying clouds appearing at high altitudes, which are closely related with the activity of South China frontal processes, especially the South China quasi-stationary fronts, and reflect on the role of local terrain as well. The heavy fogs are characteristic of long duration, extremely low visibility, well-organized lumpshaped structure, large-size fog-drops, moderate concentration, high LWC, and stronger turbulent diffusion within the fog layers than in fine sky. They differ much from radiation fogs, which are better documented in previous study in China. It is found that fog LWC is in significant anti-correlation with visibility so that large LWC is associated with small visual range. It is also noted that one of the reasons for the fluctuation of characteristic quantities of micro-structure such as the LWC of fog in the area is, in addition to the inhomogeneous structure of the fog itself, the effect of advection and inhomogeneous underlying surface; during the translation of fog with the ambient wind, irregular upslope and cross-over movement is another reason for the inhomogeneous structure and fluctuation of fog. The spectrum of the aerosol size displays itself as the power function of monotonous descent. The concentration of submicrometer particles is even higher. The high-concentration sulfate particles found in the aerosols of Nanling Mts. are actually good nuclei for condensation, which are favorable for the formation of fog. The presence of fog can help cleanse the trace compositions in the atmosphere so that fog droplets contain high levels of polluting elements. In the meantime, compared to cloud droplets, fog droplets are easier to be captured by the vertical surfaces of objects on the land surface, such as vegetation and buildings to constitute another kind of cleansing process. In vast stretches of forest like the Nanling Mts., this kind of cleansing may be quite important. Studying the characteristic variation of fogs in the area realistically assists in setting up a forecast and warning system for local fogs and provides basic information for fog dispersal experiments.