Study On Evolution Characteristics And Dynamic Estimations Of Open Biomass Burning Emissions,in China

Open biomass burning,one of the major sources of atmospheric pollutants in China,might lead to serious air pollution in a short time due to its unpredictable distributions in time and space.Historical trends and dynamic estimation of open biomass burning emission are the basis of data collection for emission characteristics and climate change analysis,as well as air quality simulation.However,current studies were either built on a single-year based open biomass burning emissions or utilizing a global-scale inventory.Thus,China still needs the dataset used for long-term emission variations characterization and key influence factor clarification.Also,China still lacks the establishment of dynamic open biomass burning emission inventory.In this study,open biomass burning emissions in China for the period of 2003-2017 were estimated by using a combination of statistical data and MODIS fire observations.Spatiotemporal variations with a long timescale and its driving forces of open biomass burning emission in China were analyzed.In response to the need for dynamic open biomass burning emission inventory,a dynamic estimation method for open biomass burning emission based on fused fires detected by polar orbit satellite(MODIS and VIIRS)and geostationary satellite(Himawari-8)observations were constructed.This study filled the shortcomings of researches about open biomass burning emissions in China.Key conclusions in this thesis are drawn as below.(1)A method combined with statistical data and long-timescale MODIS fire observations is used to estimate open biomass burning emissions,in China.(2)From 2003 to 2017,open biomass burning emissions in China were increasing in annual amounts and expanding in spatial distributions.Hot spots of emissions were mainly located in Northeast China,North China Plain and Cheng-Yu district.Open crop residue burning was the major contributor of open biomass burning emissions.(3)Among the 7 regions in China,annual emissions from open crop residue burning in Region 5 declined slightly during the study period,while emissions in other regions exhibited obvious increasing trends although there were declines in some years.For the monthly distribution of open crop residue burning emissions,emissions in each region showed regional discrepancies.(4)Natural factors,including geographical meteorological conditions,were the main driving forces of the monthly patterns of open biomass burning emissions for each region,as well as the factors that affect annual emission fluctuations in Region 4 and Region 5.The development of rural economy and the reduction of the rural population were the main reasons for the overall increasing trends of annual emissions from open crop residue burning in Region 1,Region 2,Region 3,Region 5 and Region 7.The release and implementation of policies about open burning prohibition and crop residue utilization could effectively decrease open crop residue burning emissions at national and regional levels.(5)We established a fusion method for fires detected by polar orbit satellite(MODIS and VIIRS)and geostationary satellite(Himawari-8).The fused fires had higher spatial representation and temporal resolution compared with fires observed by MODIS or VIIRS.(6)Dynamic estimations of open biomass burning emission were conducted by using a combination of fused FRE and emission coefficient of open biomass burning based on FRE.(7)Comparisons with other emissions and datasets were conducted to assess the reasonableness and reliability of the historical and dynamic emissions from open biomass burning.The spatial distribution of the dynamic emission inventory based on fused fires was more correlated with MODIS AOD than the historical emissions allocated by MODIS fires.(8)Taking Guangdong Province as an example,a case study on the development of dynamic open biomass burning emission inventory was constructed by using localized parameters for fire fusion and emission coefficient.The historical emissions from open biomass burning built in this study were the foundation for identifying the emission variations at the national level and key impact factors.Also,they were the basis of evaluating the emission situation and building the method for open biomass burning emission dynamic estimation in China.Open biomass burning emissions derived from fused fire-based may increase the temporal resolution to 1 hour with a time delay of only 1 to 2 days.At the same time,the dynamic open biomass burning emission inventory not only could improve air quality simulations and researches on climate change,but also might promote the development of the dynamic product of open biomass burning emission inventory in China.