Occurrence Characteristics Of MODIS C6 Active Fires And Its Main Influencing Factors In Mainland Southeast Asia

Fire,a fundamental component of the earth’s major terrestrial ecosystems,has significant impacts on climate change,biological diversity,regional air quality,public health,and regional economies.With the development of remote sensing,satellites acquire near-real-time fire information(active fires,including vegetation fires,urban fires,volcanic eruptions,plume,etc.)by capturing surface thermal anomalies,and generate position vector products with the occurrence location and time of active fires,which provide effective data support for the research on the occurrence and development of active fire.As a typical region of tropical monsoon climate(TMC),Mainland Southeast Asia(MSEA)has distinct dry/rainy seasons throughout the year.High temperature and little rainfall in the dry season create favorable climatic conditions for the occurrence and development of active fires in MSEA.In addition,agriculture is the economic pillar industry of MSEA,and agricultural farming in MSEA has always been accompanied by traditional fire-related farming methods such as slash-and-burn and straw burning.Taking MSEA as an example,based on the active fire products(2001—2020)of Moderate Resolution Imaging Spectroradiometer Collection6(MODIS C6)provided by the Fire Information for Resource Management System(FIRMS),the spatiotemporal dynamic characteristics of active fires,agricultural active fires(agricultural fires)and forest active fire(forest fires)in MSEA were revealed using kernel density,spatial autocorrelation and other methods(Chapter 3).The occurrence probability,occurrence intensity and its spatiotemporal distribution characteristics of active fires,agricultural fires and forest fires in MSEA were quantified and analyzed using spatial statistics and other methods(Chapter 4).Combining vegetation,terrain,climate,population,economy,traffic and other data products,the characteristics of influencing factors of active fire,agricultural fire and forest fire occurrence intensity in MSEA were identified using Geodetector.The spatial correlation characteristics between agricultural/forest fire occurrence intensity and their main factors in MSEA were studied using pearson correlation coefficient and other methods(Chapter 5).It aims to provide a scientific basis for active fire management and forecasting and carbon emissions in MSEA,as well as provide an important reference for the development of active fire remote sensing monitoring in characteristic areas.The main results show that:(1)Active fire occurrence showed clear spatiotemporal dynamics and regional differences in MSEA.Active fires,agricultural fires and forest fires all occurred in March,mainly at 6:00 GMT(13:00 local time)during 2001—2020.Spatially,active fires were more likely to occur in high elevation,backward economy,many forests and inland,and northeastern Cambodia,northern Laos,and western Myanmar were always areas with high occurrence density of active fires in the study period.(2)The occurrence probability and intensity of active fire were generally low,but showed obvious spatial characteristics in MSEA.The occurrence of active fire in MSEA was dominated by low(1/20～4/20)and comparatively low(5/20～8/20)probability during2001—2020.The intensity was dominated by weak intensity(one per year),followed by comparatively weak intensity(2～3 times/year),and the medium intensity and above(4～33 times/year)was the smallest.The occurrence probability and intensity of agricultural fire were both lower than those of forest fires.Those of agricultural and forest fires in Cambodia were stronger than those in the other four countries in the study period.(3)Human factors had a stronger influence on the intensity of active fire than natural factors in MSEA.During 2001—2020,the order of influencing factors to the intensity of active fire was: settlement density > population density > elevation > slope > road density >temperature > land cover > vegetation index > gross domestic product(GDP)>precipitation > aspect.Among them,the vegetation factors(land cover and vegetation cover)had the strongest influence on the intensity of agricultural fire,the population factors(settlement density and population density)had the strongest influence on forest fire.In addition,the settlement density had the strongest influence on the interaction of each factor.(4)The correlation between the intensity of agricultural/forest fire and population density were both high,but there were differences in other factors in MSEA.Agricultural fires mainly occurred in areas with medium vegetation index(0.45～0.65),sparse settlements,roads and population,and temperature greater than 29.9°C in MSEA.The correlation between the intensity of agricultural fire and population density was mainly strong positive correlation.Forest fires mainly occurred in gentle slope areas with sparse settlements and population,elevation greater than 500 m and less than 1000 m,and temperature greater than 29°C.The linear positive correlation between the intensity of forest fire and population density was comparatively strong,but lower than that of agricultural fire in the study period.