Abstract
Abstract. Fires affect the composition of the atmosphere and Earth's radiation balance by emitting a suite of reactive gases and particles. An interactive fire module in an Earth system model (ESM) allows us to study the natural and anthropogenic drivers, feedbacks, and interactions of open fires. To do so, we have developed pyrE, the NASA GISS (Goddard Institute for Space Studies) interactive fire emissions module. The pyrE module is driven by environmental variables like flammability and cloud-to-ground lightning, calculated by the GISS ModelE ESM, and parameterized by anthropogenic impacts based on population density data. Fire emissions are generated from the flaming phase in pyrE (active fires). Using pyrE, we examine fire occurrence, regional fire suppression, burned area, fire emissions, and how it all affects atmospheric composition. To do so, we evaluate pyrE by comparing it to satellite-based datasets of fire count, burned area, fire emissions, and aerosol optical depth (AOD). We demonstrate pyrE's ability to simulate the daily and seasonal cycles of open fires and resulting emissions. Our results indicate that interactive fire emissions are biased low by 32 %–42 %, depending on emitted species, compared to the GFED4s (Global Fire Emissions Database) inventory. The bias in emissions drives underestimation in column densities, which is diluted by natural and anthropogenic emissions sources and production and loss mechanisms. Regionally, the resulting AOD of a simulation with interactive fire emissions is underestimated mostly over Indonesia compared to a simulation with GFED4s emissions and to MODIS AOD. In other parts of the world pyrE's performance in terms of AOD is marginal to a simulation with prescribed fire emissions.
Highlights
Open biomass burning (BB), the outdoor combustion of organic material in the form of vegetation, occurs on every continent, with the exception of Antarctica, at a scale observable from space
First we want to demonstrate how the parameterization with regionally dependent fire suppression improves the simulation of fire activity compared to the original simplified global fire suppression proposed by Pechony and Shindell (2009) (Fig. 4)
We propose regional modifications to Africa (NHAF, SHAF), a region that drives global fire activity, and had a distinct mismatch in active fires compared to satellite retrievals
Summary
Open biomass burning (BB), the outdoor combustion of organic material in the form of vegetation, occurs on every continent, with the exception of Antarctica, at a scale observable from space. Open BB is perceived as a natural ecological process that has been modulating the carbon cycle for more than 420 million years (Scott and Glasspool, 2006). In practice, BB has been mediated by human activities for more than 100 000 years (Bowman et al, 2009, 2011; Archibald et al, 2012). Bellouin et al (2008) estimated that, at present, only about 20 % of fires, compared to preindustrial times, is natural. Andreae (1991) estimated that in the tropics, where about 85 % of fire emissions occurs (van der Werf et al, 2017), only 10 % of fires is natural. Humans affect fires directly through ignition and suppression and indirectly through anthropogenic changes to land surfaces and climate. According to Hantson et al (2015), land-use practices are the most important driver of human–fire interactions
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