Atmospheric particulate pollution causes a serious threat to the environment, economic, and human health. The temporal and spatial distribution of Particulate Matter (PM) obtained by remote sensing helps to study atmospheric particulate pollution study and formulate policies. In this paper, a semi-empirical method is established to estimate the Total Suspended Particles TSP mass concentration based on ground-based remote sensing. In the method, a key transformed ratio of TSP aerosol volume (V) to its optical depth (AOD) is defined aerosol Volume-to-Extinction (VE). The properties of VE are analyzed for the different aerosol types by using AErosol RObotic NETwork (AERONET) data at seven sites including Beijing (urban/industrial), GSFC (urban/industrial), CUIABA MIRANDA and Mongu (biomass burning), Solar Village (desert dust), and Ascension Island and Lanai (oceanic) sites for about 10 years. It is found that VE for different aerosol types is a function of fine mode aerosol Volume-to-Extinction VEf and coarse mode aerosol Volume-to-Extinction VEc. The VEf is a function of Fine Mode Fraction (FMF) which is put forward by Zhang and Li (2015). VEc is also put forward as a function of FMF in this study. The results show the proportion of samples with the relative error of less than 16.7% is about 64%, and that with relative error of less than 50% is approximately 92%. Combined with the other assumptions including the aerosol vertical distribution and the light extinction of water uptake, the dry TSP mass concentration near the ground can be obtained. And the similar trend of the remote sensing TSP results and the in-situ PM10 measurements in Beijing is obtained, with the correlation coefficient of 0.78.
Aerosol plays a key role in the assessment of global climate change and environmental health, while observation is one of important way to deepen the understanding of aerosol properties. In this study, the newly instrument – lunar photometer is used to measure moonlight and nocturnal column aerosol optical depth (AOD, τ) is retrieved. The AOD algorithm is test and verified with sun photometer both in high and low aerosol loading. Ångström exponent (α) and fine/coarse mode AOD (τf, τc) 1 is derived from spectral AOD. The column aerosol properties (τ, α, τf, τc) inferred from the lunar photometer is analyzed based on two month measurement in Beijing. Micro-pulse lidar has advantages in retrieval of aerosol vertical distribution, especially in night. However, the typical solution of lidar equation needs lidar ratio(ratio of aerosol backscatter and extinction coefficient) assumed in advance(Fernald method), or constrained by AOD2. Yet lidar ratio is varied with aerosol type and not easy to fixed, and AOD is used of daylight measurement, which is not authentic when aerosol loading is different from day and night. In this paper, the nocturnal AOD measurement from lunar photometer combined with mie scattering lidar observations to inverse aerosol extinction coefficient(σ) profile in Beijing is discussed.
As an active remote sensing technique, ground-based lidar can detect the backscattered signals of atmospheric cloud and aerosol layers. The measured signals can be used to obtain the vertical profile information of aerosol extinction coefficients. The atmospheric aerosol is measured in Beijing during Asia-Pacific Economic Cooperation (APEC) conference in early November 2014. Fernald method is chosen as the inversion method, and a comparison is made by using Klett’s method. Using the aerosol optical depth(AOD) measured by sunphotometer as a constraint data. The results are used for the analysis of the vertical distribution of aerosol extinction coefficients, three periods are considered, which including several days before, during and after the APEC conference. From the retrieved results of lidar measurement, it was found that the maximum value of extinction coefficients at vertical height in the beginning period reached beyond 2, but it decreased to the range of 0.05 during the conference. Then it gradually increased to more than 2 after the APEC conference. The results show that vertical distribution range of aerosol extinction coefficients decreased to 1km with increasing of AOD. The retrieved AOD results illustrate the extinction characteristics of aerosol,and it relates with the concentration distribution of atmospheric particles. According to the relationship between extinction coefficients and atmospheric visibility, the weather condition can be analyzed.
Because of the special geographical location and meteorology conditions, Beijing is a dust-prone city for a long history especially in the spring season. But these years, the most common air pollution in Beijing is haze which is mainly composed of fine particles. The dust is transported from north (Inner Mongolia province and Mongolia country), and the haze is transported from south (Hebei, Shandong and other provinces). Generally, the severities of dust and haze are opposite for the different weather causes. On March 28, 2015, the spring coming earlier for the relatively high temperature, a severe dust weather process happened suddenly in the long-term hazy days. In this dust process, the PM10 concentration was more than 1000μg/m3; the visibility was no more than 3km; and the aerosol optical depth was more than 2, which reached a severe pollution level. We used ground-based remote sensing instruments to observing the heavy dust episode. The data of two conditions were analyzed optical and microphysical parameters contrastively including the Aerosol Optical Depth, Single Scattering Albedo, Size distribution, Complex refractive index, Fine-mode Fraction. The vertical distribution characteristics were also analyzed by the lidar measurements. The results show that big differences between the dust and haze aerosol properties. But we found that fine mode particle pollution was assignable in the dust pollution weather in 2015 spring in Beijing. Our preliminary inference is that this dust episode was not only caused by transportation, but also contributed by the local raise dust.
Information on the vertical distribution of aerosol is important for understanding its transport characteristics as well as aerosol retrieval uncertainty. In this paper, the believable lidar ratio under clear sky condition during December 2014 is determined from ground-based lidar and sun-photometer site in Beijing. Then two methods are adopted to derive typical aerosol extinction profiles by averaging attenuated backscatter and retrieved extinction profiles respectively. The results indicate that the former vertical gradient of dispersion (standard deviation) is smaller than the latter. Moreover, the comparison of the aerosol extinction coefficient profiles shows a good consistency above 2km but significant difference below that altitude.
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