Development and analysis of a forest fire emission inventory in China considering daily variation patterns

Forest fire emission inventories constitute a fundamental data source for air quality modeling and investigations into the environmental impacts of forest fires. Current datasets predominantly offer daily or monthly emission estimates derived from Moderate Resolution Imaging Spectroradiometer (MODIS) fire products. However, detailed analyses of forest fire emission characteristics at the hourly resolution remain limited in China. In this study, we developed an hourly emission inventory for Chinese forest fires from 2016 to 2022 by integrating MODIS, Visible Infrared Imaging Radiometer Suite (VIIRS), and Himawari-8 active fire data, while incorporating diurnal variation patterns of forest fire activity. Utilizing this inventory, the spatial and temporal distributions of forest fire emissions across China were analyzed. The findings indicate that forest fires consumed approximately 95,495 Gg of dry matter during the study period, with the majority concentrated in the southern, southwestern, and northeastern forest regions, accounting for 44.3 %, 32.5 %, and 18.2 % of the total emissions, respectively. Emission hotspots in the southern forest region were predominantly located in provinces, such as Guangxi, Guangdong, Fujian, Jiangxi, and Hunan. In the southwestern forest region, hotspots were concentrated in southern Yunnan and Sichuan, while in the northeastern forest region, they were distributed across northeastern Inner Mongolia, northwestern Heilongjiang, and central Jilin and Liaoning. Months with higher forest fire emissions in China occur in February, March, April, October, November, and December. Significant seasonal differences exist in the diurnal variation of fire emissions across different forest regions. The Northeast Forest Region exhibits distinct emission peaks during spring and autumn, with peak times occurring at 13:00 and 12:00, respectively. The Southern and Southwest Forest Regions show similar diurnal variation characteristics. During winter, their peak emission times occur at 13:00-14:00 and 14:00-15:00, respectively. In spring and autumn, both regions display two emission troughs and three emission peaks. The occurrence times of these troughs and peaks in the Southwest Forest Region lag approximately 1 h behind those in the Southern Forest Region. These results provide critical insights into the spatiotemporal characteristics of forest fire emissions in China and offer a robust foundation for further research on the precise quantification of the air quality impacts associated with forest fires.