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Spatial-temporal Distribution of Aerosol Optical Depth over Northeastern China During 2000‒2019
HAN Yang, KANG Ling, SONG Yu
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (6): 1027-1034.   DOI: 10.13209/j.0479-8023.2021.084
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Using MCD19A2, a new product of MODIS with high temporal and spatial resolution(daily; 1 km × 1 km), spatial-temporal distribution of aerosol optical depth (AOD) over northeastern China during 2000?2019 were studied and analyzed. The results showed that the average AOD of the northeastern China in recent 20 years is 0.23, and have changed little. 2003 is the year with the highest AOD (0.38), which is mainly affected by spring drought, sand blowing, straw burning and other factors. In terms of spatial distribution, there is a decreasing trend from south to north. Liaoning province is higher than Jilin province and Jilin province is higher than Heilongjiang Province. AOD high-value areas are concentrated in the urban agglomeration of south-central region of Liaoning Province and other areas with dense population and developed industry. Low-value area is distributed in the greater Hinggan Mountains, lesser Hinggan Mountains, Changbai Mountains and other mountainous areas. Seasonal distribution of AOD; Higher in spring and summer, lower in autumn and winter. The results can be used to study the effects of aerosols on the atmospheric radiation balance or to simulate the concentration of particulate matter.
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Co-benefits of Decarbonizing China’s Transport Sector in Energy Saving and Emission Reduction under 1.5- and 2-degree Targets in 2050
LU Pantao, HAN Yalong, DAI Hancheng
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (3): 517-528.   DOI: 10.13209/j.0479-8023.2021.012
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This study evaluates the energy structure change and co-benefits in air pollution improvement in the transportation sector of China in line with the 2oC and 1.5oC targets based on an energy system optimization model IMED|TEC. The results show that under 2oC and 1.5oC targets in 2050, the energy consumption would decrease by 12% and 33% compared to the reference scenario. The energy mix would shift from traditional petroleum to cleaner biomass and even electricity or hydrogen energy. Under the 2oC scenario, biomass energy would account for 35% of the total energy consumption, whereas under 1.5oC scenario, hydrogen and electricity would account for about 67% of total energy consumption. Decarbonization of China’s transportation sector can bring significant air quality improvement. Under the 2oC scenario, CO2 emissions will be reduced by 38% in 2050, associated with reductions of NOx, SO2 and PM2.5 emissions by 35%, 34% and 38%, respectively. Under the 1.5oC scenario, the amount of pollutant emission reduction would be twice that at 2oC. However, emissions reduction rates would be quite limited for the aviation and waterway transportation sectors.
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Modelling Relationship between NDVI and Climatic Factors in China Using Geographically Weighted Regression
HAN Ya, ZHU Wenbo, LI Shuangcheng
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (6): 1125-1133.   DOI: 10.13209/j.0479-8023.2015.130
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Based on the GWR (geographically weighted regression) model supported by ArcGIS, the research explores the multi-scale relationship between vegetation change, climatic factors, and the sensitivity of vegetation to climate factors using AVHRR vegetation cover data combined with temperature and precipitation data in China from 1982–2010. Compared with the general linear regression (Ordinary Least Square, OLS) model, GWR gives a much better fitting result, with the goodness of fit increased from 0.3 to 0.6. The relationship between NDVI, annual rainfall, and average annual temperature has a significant spatial heterogeneity. Regression coefficients of climatic factors decrease from north to south and are higher in the northwest dry region of China. Temperature is more influential than rainfall on NDVI in most areas of China. Each ecological zone has different spatial scales when NDVI and the climatic factors maintain a stable relationship.

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Study on the Development Law of Structural Fractures of Yanchang Formation in Longdong Area, Ordos Basin
ZHAO Wentao, HOU Guiting, ZHANG Juzeng, FENG Shengbin, JU Wei, YOU Yuan, YU Xuan, ZHAN Yan
Acta Scientiarum Naturalium Universitatis Pekinensis    2015, 51 (6): 1047-1058.   DOI: 10.13209/j.0479-8023.2015.064
Abstract1170)      PDF(pc) (1328KB)(1112)       Save

In order to study the distribution of fracture controlled by layer thickness and lithology, clastic rock of 6-7th Member, Yanchang Formation in Longdong area is selected as investigated subject, and the areal density of their structural fractures is meassured. Measured fracture densities show that the layer thickness of clastic sequence has an effect on fracture density. Compared with thicker layer, it is easier for thinner layer to develop structural fracture, which is related to the different stress concentration near fracture tip in different layer thickness. Within a certain thickness range, fracture density has an exponential relationship with layer thickness, while the fracture density remains mostly unchanged when thickness exceeds 250 cm. Under the condition of same layer thickness and different lithology, the value of fracture densities from small to large follow the order of medium sandstone, fine sandstone, siltstone and mudstone, which means that in the same tectonic setting and layer thickness, the smaller the size range is, the larger the fracture density will be. Besides, there is an exponential relationship
between fracture density and grain size, which may be caused by the different stress between grains of different size. By multivariate statistics and mechanism analysis, layer thickness is the key factor in controlling fractures’ development compared with lithology.

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