Measurement and Modeling of CH4 and CO2 Fluxes from Local Sources Using Portable Total-Column Spectrometers

Recent studies have shown that a small group of compact solar-tracking spectrometers can detect enhancements in the total column concentrations of CO₂ and CH₄ across distances as small as a few kilometers. These measurements can be combined with an adaptation of the HYSPLIT-STILT modeling framework and high-resolution emissions inventories to estimate carbon fluxes from local sources. Short term field campaigns using sets of these spectrometers (Bruker model EM27-Sun) have been performed in cities such as Boston, Indianapolis, and San Francisco. The transport model is then used to both quantify and attribute both thermogenic and biogenic carbon emission sources. These campaigns used arrays of 2 to 5 sensors spaced throughout the domain of each city, and measurements were made for several days over the course of a few weeks. Biological fluxes have also been estimated for the Tanana Valley of Alaska using data collected during an EM27-Sun field campaign in the summer 2016, combined with high-resolution vegetation maps. The deployment of small networks of these types of sensors, and the accompanying modeling framework, represent a new way to quantify carbon emissions in domains that are larger than point sources, and smaller than what is typically considered regional scale. An understanding of changes in total-column concentrations across small domains is also important in the interpretation and validation of carbon satellites such as OCO-2.