Expanding the Boston Region Carbon Monitoring System: The Addition of Total Column Observations of Greenhouse Gases
Abstract
The city of Boston and the State of Massachusetts have ambitious goals to reduce greenhouse gas emissions. Assessing the efficacy of mitigation policies aimed at meeting these goals requires traceable methods for tracking actual changes in emissions. Eastern MA is one of the best instrumented and closely studied regions for CO2 and CH4 on the globe with a network of ground stations running continuously since 2013. Combining well calibrated atmospheric observations with new highly resolved biological and fossil fuel emissions flux models in a high-resolution inverse model framework has enabled us to constrain fluxes of CH4 and CO2 in greater Boston. Average anthropogenic CO2 emissions in the region were 0.92 kg C·m-2·y-1, with 18% uncertainty. The modeled CO2 enhancement showed excellent correlation with observations on daily and weekly timescales (R2 = 0.67 for daily afternoon averages, R2 = 0.81 for 7-day running average). Starting in 2015 two solar-observing Bruker EM27/SUN Fourier transform spectrometers were added to our carbon monitoring system to provide information on the total atmospheric columns of XCO2, XCH4, and XCO. The addition of EM27/SUNs enables us to continually observe column-averaged concentrations of GHGs both inside the urban core (at Cambridge, MA) and in the air entering the region (at Harvard Forest; Petersham, MA) during sunlit hours. Total column data is less sensitive to model errors in vertical mixing, and more directly comparable to the data obtained by the new generation of satellite sensors including TROPOMI and OCO-3. Summertime values of XCO2 at Harvard Forest show a clear diel cycle in the growing season: high morning values reflect accumulation of respired CO2 overnight, decreasing during the day due to photosynthetic uptake averaging -0.3 (as much as -0.5) ppm/hour. This uptake drives a diel cycle in the urban-rural gradient of XCO2 which must be quantified in order to accurately separate out anthropogenic emissions. These column data are currently being added to our high-resolution inverse model framework along with tower measurements, Lidar observations, and, critically, a carefully constructed spatially resolved prior model of emissions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B33A..07H
- Keywords:
-
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 6309 Decision making under uncertainty;
- POLICY SCIENCES;
- 6620 Science policy;
- POLICY SCIENCES & PUBLIC ISSUES