Calculating Carbon Emissions for Wildfires during FIREX-AQ 2019

Abstract:

In order to understand the impact wildfires have on air quality and human health, it is necessary to quantify the carbon they release into the atmosphere, and the relative influence both flaming and smoldering fire processes have on these emissions. During the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign, approximately 40 Wildfires in the Western United States were sampled by NOAA and NASA platforms to investigate the impact wildfires have on air quality and climate. Our group, Fuel-2-Fire, aims to connect the fuel and fire conditions to the emission of carbon into the atmosphere as well as the efficacy of satellite data for estimating burned area in emissions calculations. Our goal is to accurately estimate daily and 1-second carbon emissions for each sampled fire in the campaign. These estimates can then be used to compare with in-situ measurements of biomass burning aerosols sampled on the aircraft and mobile platforms.

This emissions product we’ve developed uses a ground-based calculation approach, which incorporates satellite information, fuelbed data, and Fire Danger to estimate daily carbon emissions. Daily carbon emissions are calculated using: 1) daily burned area; 2) the amount of biomass present as available fuel; 3) the fraction of carbon present in biomass; and 4) the amount of fuel consumed (based on fire weather). MODIS (1 km) and VIIRS (375 m) satellite fire detections are used to estimate new and residual burned area each day. We define ‘residual burned area’ as area burning in a region that has burned on a previous day. Biomass available for consumption is estimated using the Fuel Characteristic Classification System (FCCS) 30 m fuelbeds, and the Fire Danger rating from WFAS is used to determine consumption. Finally, flaming to smoldering percentages are allocated for new and residual burned area based on Fire Danger rating. The total carbon emissions estimates are distributed throughout the day using a probability distribution of fire activity derived from 5-min GOES Fire Radiative Power observations, which can then be used to compare to aircraft-sampled emissions. Preliminary comparisons between our emissions estimates and in situ measurements of CO₂, CO, and black carbon aerosol show strong agreement.