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Measurements at BAO Tower for the Carbon Tracker Observing Network

May 30, 2007

The Earth System Research Laboratories (ESRL) has recently begun making continuous measurements of atmospheric carbon dioxide and carbon monoxide at the Boulder Atmospheric Observatory (BAO) 300m tower in Erie, CO. The BAO site is the latest addition to ESRL's Carbon Tracker Observing Network. Because of its proximity to the Denver metropolitan area, measurements from the BAO tower will provide detailed information about urban and industrial sources of CO₂.

Background:
ESRL's Global Monitoring Laboratory (GMD) began making measurements from tall towers in the 1990s in order to extend long-term carbon-cycle gas monitoring to continental areas. Existing television and radio towers are utilized as sampling platforms for in-situ and flask sampling of CO₂ and other atmospheric trace gases. Carbon dioxide is the principal carbon greenhouse gas, and measurements of its abundance are sensitive to upwind fluxes including fossil fuel emissions and uptake and release by vegetation and soils. Carbon monoxide is an indicator of combustion, and elevated levels can result from urban or industrial emissions or from biomass burning. CO data contribute to the interpretation of CO₂ measurements by helping to identify and quantify pollution episodes. GMD's tall tower sites are principal components of ESRL's Carbon Tracker Observing Network.

The BAO tower has been operated by the ESRL Physical Sciences Laboratory (PSL) since the 1970s and serves as a unique facility for monitoring the Earth's atmospheric boundary layer. In addition to the new BAO site, the network includes three other tall tower sites, and plans call for the addition of eight more towers distributed throughout the continental US over the next several years.

Significance:
Data collected from the BAO tower will contribute to the North American Carbon Program, a multi-agency effort to improve understanding of the carbon cycle. The data represent an important new constraint for ESRL's Carbon Tracker CO₂ assimilation system and will improve NOAA's ability to reliably estimate surface sources and sinks of CO₂. Detailed knowledge about the carbon cycle is essential for understanding and predicting global climate change. These activities advance NOAA's mission goal of understanding climate variability and change in order to enhance society's ability to plan and respond.