Investigating the trace gas emissions of biomass burning in the Earth system

Project Highlights:
• Use satellite data to quantify the amounts of pyrogenic trace gases present in plumes associated with biomass burning.
• Use satellite data and chemical transport models to provide estimates of the emissions of species from biomass burning.
• Acquire a set of skills to create and analyse remote-sensing datasets.
Overview:
Biomass burning, the combustion of vegetation on the Earth’s surface, is a major source of particulate matter and trace gases in the atmosphere. Although fire in the Earth system can be a natural process, e.g. lightning-initiated, the majority of it is anthropogenic, e.g. for land clearing. The emissions from fires contribute to climate change and public health issues, however these emissions are not well constrained.
Satellite remote sensing is the best method to acquire quantitative information on the global magnitude and spatial distribution of biomass burning. From space one can observe fire activity via products such as fire radiative power (FRP), a measure of the rate of radiant heat output from a fire.
In addition, remote sensing generates data on species emitted into the atmosphere. The two Infrared Atmospheric Sounding Interferometer (IASI) instruments, on board the MetOp-A and MetOp-B satellites (a third should be launched in October 2018), detect trace gases in the atmosphere using their distinctive spectral infrared fingerprints, thereby allowing us to track biomass burning plumes as they spread further into the atmosphere. Monitoring plumes from satellite provides a global coverage not otherwise possible, with a high density of data.
This project involves using both full optimal estimation and fast linear retrieval schemes to provide quantitative information for a number of pyrogenic species, and provide better constraints on their pyrogenic emissions.

The analysis of satellite data for pyrogenic species present in individual plumes will focus on enhancement ratios relative to the reference species carbon monoxide (a reasonably long-lived species associated with biomass burning). These are related to the ongoing chemistry within the plume at the time of measurement. However, in order to estimate atmospheric emissions for these species one needs to know their emission factors, i.e. a measure of the quantity released into the atmosphere for every unit of biomass burned. These emission factors can be calculated from measurements at the time of emission, or, if not possible, derived from enhancement ratios by taking into account the decay of the chemical species, i.e. using atmospheric models.

Methodology:
The student will identify fires from satellite FRP products, e.g. MODIS, and correlate these with trace gases present in plumes as measured by IASI.
The student will calculate enhancement ratios relative to CO for pyrogenic species present in individual plumes. Emission factors will be derived from these enhancement ratios by taking into account the decay of the chemical species. The latter will be achieved by running simulations of the TOMCAT 3D chemistry transport model (CTM) in collaboration with researchers at NCEO-Leeds.
The student will also classify plumes and their enhancement ratios / emission factors with the type of fuel burned. This will make use of simple dispersion models such as NAME or HYSPLIT.
Finally, the student will use INVICAT, a variational (4D-VAR) inverse transport model based on TOMCAT, to perform inversions of the plume trace gas data and provide better constraints on their emissions.