Estimation of emissions from biomass burning in China (2003-2017) based on MODIS fire radiative energy data

Biomass burning plays a significant role in air pollution and climate change. In this study, we used a method based on fire radiative energy (FRE) to develop a biomass burning emission inventory for China from 2003 to 2017. Daily fire radiative power (FRP) data derived from 1 km MODIS Thermal Anomalies/Fire products (MOD14/MYD14) were used to calculate FRE and combusted biomass. Available emission factors were assigned to four biomass burning types: forest, cropland, grassland, and shrubland fires. The farming system and crop types in different temperate zones were taken into account in this research. Compared with traditional methods, the FRE method was found to provide a more reasonable estimate of emissions from small fires. The estimated average annual emission ranges, with a 90% confidence interval, were 91.4 (72.7-108.8) TgCO(2) yr(-1), 5.0 (2.3-7.8) TgCO yr(-1), 0.24 (0.05-0.48) TgCH(4) yr(-1), 1.43 (0.53-2.35) TgNMHC yr(-1), 0.23 (0.05-0.45) TgNO(x) yr(-1), 0.09 (0.02-0.17) TgNH(3) yr(-1), 0.03 (0.01-0.05) Tg SO2 yr(-1), 0.04 (0.01-0.08) Tg BC yr(-1), 0.27 (0.07-0.49) TgOC yr(-1), 0.51 (0.19-0.84) TgPM(2.5) yr(-1), 0.57 (0.15-1.05) Tg PM10 yr(-1), where NMHC, BC, and OC are nonmethane hydrocarbons, black carbon, and organic carbon, respectively. Forest fires are determined to be the primary contributor to open fire emissions, accounting for 45% of the total CO2 emissions (average 40.8 Tg yr(-1)). Crop residue burning ranked second place with a large portion of 39% (average 35.3 Tg yr(-1)). During the study period, emissions from forest and grassland fires showed a significant downward trend. Crop residue emissions continued to rise during 2003-2015 but dropped by 42% in 2015-2016. Emissions from shrubland were negligible and little changed. Forest and grassland fires are concentrated in northeastern China and southern China, especially in the dry season (from October to March of the following year). Plain areas with high crop yields, such as the North China Plain, experienced high agricultural fire emissions in harvest seasons. Most shrubland fires were located in Yunnan and Guangdong provinces. The resolution of our inventory (daily, 1 km) is much higher than previous inventories, such as GFED4s and GFASv1.0. It could be used in global and regional air quality modeling.