"The emissions from open fire (e.g. forest fire, grass fire and field crop residue burning) play an important role in climate change and the atmospheric environment," Song Yu of Peking University told environmentalresearchweb. "A reliable emission inventory with high temporal spatial resolution is in high demand for atmospheric chemistry and transport simulation."
The prevailing inventory of burning emissions for Asia was developed by Streets et al in 2003 based on data for the 1950s to 1990s; it has been widely used in air quality modelling.
Nonagricultural fires have dropped sharply in Asian countries since the 1990s as governments have made efforts to restrict human practices that cause wildfires, to prevent pollution, health problems and economic and environmental losses. So Yu and colleagues felt that a new emissions inventory was needed. With this in mind, they used burned area product data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua satellites. MODIS is able to map rapid changes in surface reflectance, an indication that areas have been burned.
Because the burned area product data has a resolution of 500 m it can miss burning of field-crop residues, which tend to be small areas. As a result, the researchers focused on estimating nonagricultural open fire emissions. To assess emissions, they combined the burned area product (MCF45A1) data with estimates and measurements of fuel load, combustion factor and emission factor.
The study area extended from the west of Pakistan to the east of Japan, and from the north of Mongolia to the south of Indonesia; the results can be seen in Environmental Research Letters (ERL).
"The emissions from nonagricultural fire estimated in our study were much less than that in the prevailing burning emission inventory developed by Streets et al," said Yu. "For example, CO emissions from forest and shrubland/grasslands regions were 3.2 and 2.9 Tg per year in this study, only 10% and 30% of the prevailing emission inventory. The findings show that the wildfire occurrence in Asian countries has decreased sharply, especially over the last two decades."
The annual mean MCD45A1 burned area from 2000–2009 was 105681 sq km per year. India led the field, with 33% of the total burned area, followed by Myanmar (16%), Cambodia (11%), China (11%) and Mongolia (11%). Indonesia was the most important contributor to fire emissions, largely because of peat burning, although the country accounted for only about 2% of the burned area.
The main vegetation class burned was cropland, followed by grassland, forest and shrubland. The bulk of nonagricultural fire emissions was due to forested land because of the high biomass density of forest.
Yu says that the new nonagricultural-emissions data could be used in research on climate change and the atmospheric environment for recent open fire activities in Asia.
"We wish to renew the prevailing burning emission inventory developed by Streets et al by using our results in atmospheric chemistry modelling in East Asia," said Yu. "Our dataset was released by ERL, anyone who is interested in it can download the data from the ERL website."
• ERL, environmentalresearchweb's sister product, now offers all authors the option to publish their raw data as supplementary data material alongside their article if they wish to.