New Results from the NOAA ESRL Collaborative Tall Tower Network for Monitoring Carbon Dioxide and Related Gases
A.E. Andrews1, J.D. Kofler2, J.C. Williams3, M.E. Trudeau4, P.S. Bakwin1, C. Zhao2, K.A. Masarie1, D.H. Neff2, D.R. Kitzis2, P.P. Tans1, K.J. Davis5, A.R. Desai6, S.C. Wofsy7, W.J. Munger7, D.J. Wolfe1, M.L. Fischer8, M.J. Parker9, S.D. Wekker10, C.O. Stanier11, G. Petron2, A.M. Michalak12, J. Eluszkiewicz13, T. Nehrkorn13, K.R. Gurney14, W. Peters15 and A.R. Jacobson2
1NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305; 303-497-6773, E-mail: Arlyn.Andrews@noaa.gov
2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309
3Science and Technology Corporation, Boulder, CO 80305
4Cooperative Institute for Research in Atmospheres, Colorado State University, Fort Collins, CO 80521
5Department of Meteorology, Penn State University, University Park, PA 16802
6University of Wisconsin, Madison, WI 53706-1481
7Harvard University, Cambridge, MA 02138
8Lawrence Berkeley National Laboratory, Berkeley, CA 94720
9Savannah River National Laboratory and Savannah River Nuclear Solutions LLC, Aiken, SC 29808
10University of Virginia, Charlottesville, VA 22904
11University of Iowa, Iowa City, IA 52242
12University of Michigan, Ann Arbor, MI 48109
13Atmospheric and Environmental Research, Inc., Lexington, MA 02421-3136
14Purdue University, West Lafayette, IN 47907
15Department of Environmental Sciences, Wageningen University & Research Center, Wageningen, Netherlands
NOAA ESRL began making measurements from tall towers in the 1990s in order to extend long-term carbon-cycle gas monitoring to continental areas. Existing television, radio and cell phone towers are utilized as sampling platforms for in situ and flask sampling of CO2 and other atmospheric trace gases, including CO. Tall tower CO2 mixing ratio measurements are sensitive to upwind fluxes over scales of hundreds of kilometers. Such measurements therefore place strong constraints on estimates of regional scale carbon budgets. CO 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. The tall tower sites are part of the North American Carbon Program and are a primary data source for ESRL's CarbonTracker CO2 data assimilation system. The network has become a highly collaborative enterprise, with contributions from a host of university, private sector, and government partners. The sites are equipped with high-precision semi-continuous CO2 and CO analyzers, and most also have automated flask sampling equipment that collects an air sample approximately once per day. We will present important features of the data from each site, including seasonal and diurnal cycles and daytime vertical gradients for CO2 and CO. We have used the Stochastic Time Inverted Lagrangian Transport model to compute sampling footprints for each site. The footprints are combined with optimized fluxes from CarbonTracker and with the Vulcan inventory to estimate the contributions of ecosystem, fire, ocean and fossil fuel fluxes.
Figure 1. The mean seasonal cycle of CO2 observed at the tall towers. An estimated background value representing the CO2 concentration before the air encountered the continent was subtracted from the data in order to isolate the variability associated with North American emissions and uptake. The result is the signal that drives data assimilation and inverse model estimates of the North American carbon budget.