Combining measurements and modeling to quantify power plant contributions to atmospheric NO2 and CO2

Successful adoption of international agreements to limit CO₂ emissions requires sound methods to measure and monitor anthropogenic sources of this green house gas. However, the task of verifying compliance to such agreements is very difficult. CO₂ is a naturally abundant and variable atmospheric constituent and small increases need to be measured against this high background level. Because CO₂ is a long-lived gas, background levels are also rising. Emissions inventories derived from fossil fuel consumption data are uncertain and can be subject to manipulation. To ensure fair compliance, remotely sensed measurements and an understanding of the transport of CO₂ from the sources are required.

We will discuss a new multi-scale approach to address this issue that combines in-situ and remotely sensed CO₂ measurements along with numerical model simulations to identify emissions from fossil fuel energy sources. Our approach takes advantage of co-emitted chemicals (e.g. NO₂, SO₂, and CO), which are more easily measured against their relatively low background concentrations. The emissions ratio of these signature species to CO₂ is also characteristic of the fuel and combustion process used by the emitting energy sector.

We will present early results from our study in the vicinity of the Four Corners and San Juan power plants, which have well-documented emissions. Trends in NO₂ emissions as identified by Ozone Monitoring Instrument (OMI) on the Aura satellite and global GEOS-Chem model output analyses show the NO₂ reductions from environmental upgrades at the San Juan power plant. Remotely sensed measurements of the area by both satellites and Fourier Transform Spectrometer (FTS) are compared to simulations with the Weather Research and Forecasting model with chemistry (WRF-Chem) to infer emissions and also track the plumes emitted by these sources that are the primary air-pollutants in this region.