A process-based fire parameterization of intermediate complexity in a Dynamic Global Vegetation Model

[摘要] A process-based fire parameterization of intermediate complexity has beendeveloped for global simulations in the framework of a Dynamic Global Vegetation Model (DGVM) in an Earth System Model (ESM). Burned area in agrid cell is estimated by the product of fire counts and average burned areaof a fire. The scheme comprises three parts: fire occurrence, firespread, and fire impact. In the fire occurrence part, fire counts ratherthan fire occurrence probability are calculated in order to capture theobserved high burned area fraction in areas of high fire frequency andrealize parameter calibration based on MODIS fire counts product. In thefire spread part, post-fire region of a fire is assumed to be elliptical inshape. Mathematical properties of ellipses and some mathematical derivationsare applied to improve the equation and assumptions of an existing firespread parameterization. In the fire impact part, trace gas and aerosolemissions due to biomass burning are estimated, which offers an interfacewith atmospheric chemistry and aerosol models in ESMs. In addition, flexibletime-step length makes the new fire parameterization easily applied tovarious DGVMs.

Global performance of the new fire parameterization is assessed by using animproved version of the Community Land Model version 3 with the Dynamic Global Vegetation Model (CLM-DGVM). Simulations are compared against thelatest satellite-based Global Fire Emission Database version 3 (GFED3) for1997–2004. Results show that simulated global totals and spatial patternsof burned area and fire carbon emissions, regional totals and spreads ofburned area, global annual burned area fractions for various vegetationtypes, and interannual variability of burned area are reasonable, and closerto GFED3 than CLM-DGVM simulations with the commonly used Glob-FIRM fireparameterization and the old fire module of CLM-DGVM. Furthermore, averageerror of simulated trace gas and aerosol emissions due to biomass burning is7% relative to GFED3. Results suggest that the new fire parameterizationmay improve the global performance of ESMs and help to quantifyfire-vegetation-climate interactions on a global scale and from an Earthsystem perspective.

[学科分类] 地球化学与岩石