The AMT site uses a 107m Unicel cellular telephone transmitter tower near Argyle, Maine. This site was instrumented in September 2003 in time for the CO2 Airborne Budget and Regional Airborne (COBRA) - Maine Study, which occurred during summer 2004.
Partners:

• University of Maine (John Lee),
• USDA Forest Service Northern Research Station (David Hollinger),
• Harvard Univerisity (Steve Wofsy, Bill Munger)

The Boulder Atmospheric Observatory (BAO) tower has been operated by the ESRL Physical Sciences Division (PSD) since the 1970s and serves as a unique facility for monitoring the Earth's atmospheric boundary layer. Instrumentation for monitoring CO2 and CO was installed in April 2007. 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.

The WITN-TV transmitter tower was the first tall tower measurement site in the GMD network. Measurements began in June, 1992, with continuous monitoring of CO2 and 222Rn mixing ratios, wind speed and direction, temperature, and relative humidity at 51, 123 and 496 m above the ground. Unfortunately, our work at the WITN tower site had to be discontinued in June 1999 because the tower owner need the space that was occupied by our equipment in order to install an HDTV transmitter, as mandated by Congress. We thank American Family Broadcasting for hosting our measurements for 7 years.

The 447-m tall WLEF-TV transmitter tower in northern Wisconsin became the second site for the tall tower program in October, 1994. This tower is owned by the State of Wisconsin Educational Communications Board. A large program has evolved around our measurements at the WLEF tower, involving a number of university and federal research institutions. The goals are to assess the carbon budget of the forests in the region (the Chequamegon National Forest), and to examine the influence of forest/atmosphere CO2 exchange on CO2 mixing ratios within and above the atmospheric boundary layer over the continent. This program is known as the Chequamegon Ecosystem-Atmosphere Study (ChEAS). The ChEAS project is also a part of the AmeriFlux program. Scientists from Caltech and NASA JPL began making total column CO2 measurements at the base of the WLEF tower in 2004 by FTIR spectroscopy. These measurements are part of the validation effort for NASA's Orbiting Carbon Observatory to be launched in 2008.
Partners:

• Penn State University (Ken Davis),
• University of Wisconsin (Ankur Desai),
• USDA Forest Service Northern Research Station (Ron Teclaw and Dan Baumann)

NOAA/ESRL began continuous measurements of CO₂ and CO at the "South Carolina Tower" in August 2008 as part of a partnership with the Department of Energy Office of Science to expand carbon cycle research at the Savannah River Site.  The SCT site takes advantage of a pre-existing comprehensive meteorological network in the region that is operated by the Savannah River National Laboratory. The SRNL network includes 3-dimensional sonic anemometers and fast response CO2 and H2O sensors at each of the sampling heights on the tower that are now also used for the NOAA CO2 and CO measurements.  This location samples the southeastern US within a mixed use agricultural, residential, and industrial zone.
Partners:

• Savannah River National Laboratory (Matt Parker),
• University of Georgia (Professor Monique LeClerc)

The STR tower was instrumented in September 2007 through a collaborative effort with the Deparment of Energy's Lawrence Berkeley National Laboratory. The California Energy Commission is funding the project through its Public Interest Energy Research Program. The Sutro Tower is a San Francisco landmark and is our first site located in an urban center. STR is instrumented with automated flask sampling systems that provide daily measurements of a suite of greenhouse gases, carbon isotopes, halocarbons and other compounds.
Partners:

• DOE Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory (Marc Fischer)

Instrumentation was installed on the KWKB-TV tower in July 2007. The WBI site samples agricultural ecosystems in the corn belt. Summertime CO2 levels in this region are among the lowest in North America due to strong uptake by corn and other crops. We expect to see interannual variability in the CO2 seasonal cycle that is related to crop yields, which are carefully tracked. For example, 2007 is expected to be a record corn crop, as demand has increased for production of biofuels.
Partners:

• University of Iowa (Charles Stanier)

The WGC tower was instrumented in September 2007 through a collaborative effort with the Deparment of Energy's Lawrence Berkeley National Laboratory. The California Energy Commission is funding the project through its Public Interest Energy Research Program. The WGC site is equipped to provide continuous measurements of CO2, CO and CH4. WGC is the first tall tower site with continuous CH4 measurements. WGC is instrumented with automated flask sampling systems that provide daily measurements of a suite of greenhouse gases, carbon isotopes, halocarbons and other compounds.
Partners:

• DOE Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory (Marc Fischer)

Sensors were installed on the KWKT-TV transmitter tower in February 2001. In May 2006, this site became the first to use our newly redesigned instrumentation suite. The upgrades were made in time for the Texas Air Quality Study 2006 . We also carried out a demonstration study during 2006 where an O3 sensor was mounted at our highest sampling level (457 m above ground level). The O3 data showed clear evidence of nighttime transport of ozone in the nocturnal jet at the top of the planetary boundary layer. This site periodically samples air that has passed over the Dallas - Fort Worth and Houston metropolitan areas. At other times, the site samples relatively clean air from the Gulf of Mexico. Summertime weather patterns are dominated by a monsoonal circulation over the Gulf. WKT thus provides a measurement of the initial CO2 concentration for air passing over the continent from the south. As air moves northward, the CO2 concentration is modified by the action of sources (fossil fuel combustion, plant respiration, biomass burning, cement production) and sinks (photosynthesis).
Partners:

• Blackland Research and Extension Center-Texas Agricultural Experiment Station (Onyango Okello)