Aerosol Optical Depth:Remote Sensing Retrieval And Analyzing Characteristics Of The Spatial-temporal Distribution Over Anhui And Surrounding Areas

Based on the MODIS and HJ-1 satellite images, this paper was aimed at retrieving the aerosol optical depth, and validating its applicability using Aerosol Robotic Network (AERONET) data. This study also conducted the spatial and temporal distribution of aerosol and discussed the possible impact of the relevant influencing factors over Anhui and surrounding areas, with Aqua/MODIS aerosol optical depth monthly and yearly aerosol products released by National Aeronautics and Space Administration (NASA), Global Digital Elevation Map (GDEM) topographical data in eastern China and AERONET meteorological monitoring data as reference. Analyzing the relevance of aerosol optical depth and PM2.5 and between aerosol optical depth and PM10, also discussing their fitting models using pollutants real-time monitoring data in Hefei. Conclusions can be obtained as follows:1. AERONET aerosol monitoring data and MODIS aerosol products showed a fair good consistency in the study region, their correlation coefficient was 0.83, the slope was 0.96, and the standard deviation was 0.18. According to the standard error line defined by NASA,70% of the results data were within MODIS error range, which fulfilled the requirements of NASA error. The experimental results of the retrieval of aerosol optical depth based on HJ-1 satellite images under the different aerosol modes reflected the correlation coefficient between urban type aerosol optical depth and ADRONET monitoring data was 0.896, indicating that aerosol optical depth retrieval results based on city mode and AERONET aerosol monitoring data showed a good consistency. However, the correlation coefficient between continental type aerosol optical depth retrieval and ADRONET monitoring data was only 0.578, also 35% of the results data were within MODIS error range. In conclusion, the city mode was more suitable for the retrieval of aerosol optical depth based on HJ-1 satellite images in Hefei.2. This paper analyzes the temporal distribution of aerosol optical depth from three perspectives, using MODIS 04 aerosol products, topographical data in eastern China and Angstrom wavelength exponent, and other relevant factors. Anhui and the surrounding areas had significant spatial and temporal distribution of aerosols variation. Temporally, in spring and winter the higher concentration of aerosols was observed in northern and central Anhui, and the western Anhui showed highest mean (even higer than 0.9) in winter; while the lowest mean aerosol concentrations occured in the fall in Anhui and the surrounding areas. Spatially, the distribution of the aerosol distributed basically low in mountainous of the higher elevations, such as West Anhui, South Anhui and Mountain Lushan. Whereas a high value distribution of aerosols showed in th plains, due to the impact of mountainous barrier, resulting the aerosol concentrations in the palins along the river are significantly higher among the West Mount and the South Mount.3. Based on the retrieval of aerosol optical depth using MODIS satellite images, this paper then conducted an analysis of the correlation between aerosol and its influencing factors, which were meteorological monitoring data from real-time monitoring meteorological sites in Hefei and AERONET monitoring sites in eastern China, and the Anhui Province Almanac of 2014 and 2015. In Anhui and the surrounding areas, the visbility gradually decreased with the aerosol concentration increased. Relative humidity and aerosol optical depth showed obvious positive correlation. When the wind speed reached a certain value, it would play a catalytic role in the spread of the aerosol, thereby reducing the concentration of aerosols. Economic development and human activities in the area of intense aerosol concentrations were usually higher, while in the areas of higher mountains and higher vegetation covered, and sparsely populaed and economically backward regions, the aerosol concentrations were generally lower.4. Combined the aerosol optical depth inversed by HJ-1 satellite images with the PM2.5 and PM10 monitoring data in Hefei, the analysis that the correlation between aerosol optical depth and particulate matter and the discussion that the differences of the mean aerosol optical depth between the roads, the blocks and the integral level of Hefei had been made. The results showed that, the aerosol optical depth and PM2.5 particulate matter had shown a significant negative correlation, a negative correlation had also been shown between the aerosol optical depth and PM10 particulate matter. Between the two kinds of particulate matter, the PM2.5 particles pronounced more significant negative consistency with the aerosol optical depth, thus we can infer that the impact of atmospheric fine particles of particulate matter to be more important for the concentrations of aerosol optical depth. By extracting the aerosol optical depth to the extent of the roads and the blocks, which were compared with the integral level of Hefei, we came to the conclusion that the aerosol pollution over roads and blocks was more serious than the overall level of Hefei.