A process-based fire parameterization of intermediate complexity in a Dynamic Global Vegetation Model
1International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2Terrestrial Sciences Section, Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA
Abstract. A process-based fire parameterization of intermediate complexity has been developed for global simulations in the framework of a Dynamic Global Vegetation Model (DGVM) in an Earth System Model (ESM). Burned area in a grid cell is estimated by the product of fire counts and average burned area per fire. The scheme comprises three parts: fire occurrence, fire spread, and fire impact. In the fire occurrence part, fire counts rather than fire occurrence probability is calculated in order to capture the observed high burned area fraction in regions where fire occurs frequently. In the fire spread part, post-fire region of a fire is assumed to be elliptical in shape. Mathematical properties of ellipses and mathematical derivation are applied to remove redundant and unreasonable equation and assumptions in existing fire spread parameterization. In the fire impact part, trace gas and aerosol emissions due to biomass burning are estimated, which offers an interface with atmospheric chemistry and aerosol models in ESMs. In addition, flexible time-step length makes the new fire parameterization easily applied to various DGVMs.
Global performance of the new fire parameterization is assessed by using an improved version of the Community Land Model version 3 with the Dynamic Global Vegetation Model (CLM-DGVM). Simulations are compared against the latest satellite-based Global Fire Emission Database version 3 (GFED3) for 1997–2004. Results show that simulated global totals and spatial patterns of burned area and fire carbon emissions, global annual burned area fractions for various vegetation types and interannual variability of burned area are in close agreement with the GFED3, and more accurate than CLM-DGVM simulations with the commonly used Glob-FIRM fire parameterization and the old fire module of CLM-DGVM. Furthermore, the average relative error of simulated trace gas and aerosol emissions due to biomass burning is 7 %. Results suggest that the new fire parameterization may improve the global performance of ESMs and help to quantify fire-vegetation-climate interactions on a global scale and from an earth system perspective.