Carbon dioxide fluxes in a suburban area of Baltimore, MD: 2002–2004

Measurements of surface-atmosphere fluxes of carbon dioxide (FCO2) in urban environments are rare even though cities are an important source of atmospheric CO2 (Vogt et al. 2003). As part of the Baltimore Ecosystem Study, eddy covariance instrumentation is mounted at 41.2 m to continuously measure earth-atmosphere exchanges of carbon dioxide at the local scale in a suburban environment in Baltimore, MD. Several features make this research unique: 1) for an urban area, the study site is extensively vegetated, 2) the period of record (2002-2004) is among the longest available for urban FCO2 measurements, 3) both closed-path and open-path infrared gas analyzers are used for observations, and 4) several unique data quality control and gap-filling methods are developed for use in an urban environment. Additionally, detailed surface datasets and GIS software are used to perform flux source area analysis. FCO2 is found to be very dependent on source area land-cover characteristics, particularly the proportion of vegetated and built surfaces in the source area. Over the course of a year, the urban surface is also found to be a strong net source of CO2, though there is considerable inter-annual variability depending on environmental conditions (e.g. average temperature, total precipitation, cicada infestation). During the growing season, there is net uptake of CO2 by the surface, but this uptake is less than in forested areas and is not enough to offset CO2 emissions for the entire year.