An inversion analysis of carbon dioxide emission from airborne sampling of the 2013 Yosemite Rim Fire and its relationship with combustion phase

Abstract:

Fires from biomass burning are responsible for emitting large quantities of trace gases (e.g., carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO)) and particulate matter, which are of great importance for air quality, climate forcing and biogeochemical cycles. On average wildfires emit about 290 Tg CO2 per year in the United States, equivalent to 4-6% of annual anthropogenic emissions. Characterization of wildfire emissions is crucial for understanding the atmospheric trace gas budget and variability, and the quality of these characterizations depends on accurate gas concentration measurements associated with fuel type, meteorological conditions and fire combustion phase. The 2013 Yosemite Rim Fire was sampled by the NASA Ames Alpha Jet Atmopsheric eXperiment (AJAX) during two fire burning stages: intensive burning phase on August 29 and smoldering phase on September 10. The AJAX trace gas measurements (CO2, CH4 and ozone (O3)) provide a unique opportunity to conduct an inverse analysis of the fire emissions of key trace gases and linkage with the dynamic nature of wildfires. This study proposes to use a coupled Eulerian-Lagrangian atmospheric transport model, WRF-STILT, along with estimates of fossil fuel emissions and atmospheric CO2 background, and the latest wildfire emission inventories, to determine the contribution of the Rim Fire to atmospheric CO2. WRF-STILT is used to establish the source-receptor relationship of CO2 under different model configurations in order to bracket the transport model uncertainty. Observationally constrained CO2 emission rates will be obtained by improving the model fit to flight measurements, and the associated uncertainties with a priori and model errors will be evaluated. The model/measurement data setup and initial results of this study will be presented.