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The top panel shows the spatial distribution of averaged CO2 at 1 m above the ground over about a 1 km x 1km area and the bottom panel shows the CO2 along the distance across Como Creek (140 m). The plot demonstrates that nighttime CO2 accumulation was transported toward low lying grounds, even toward the 2-m-wide creek along the main slope; however, the spatial distribution of CO2 was also affected by low respiration from the water and local mixing generated by the thermal contrast between the water and its surrounding land, leading to low CO2 right above the water (not included in the top panel). |
NCAR was one of the hosts of the seventh International Carbon Dioxide Conference. Measurements and instrument development projects have provided key NCAR contributions to the multi-agency North American Carbon Program (NACP) and CarboEurope. These projects include:
Rocky RACCOON
The Regional Atmospheric Continuous CO2 Network in the Rocky Mountains expands the CO2 monitoring network to the western U.S. to include four sites installed in fall of 2005 and spring of 2006: Niwot Ridge T-Van (NWR), near Ward, Colorado; Storm Peak Laboratory (SPL) near Steamboat Springs, Colorado; Fraser Experimental Forest (FEF), near Fraser Colorado; and Hidden Peak (HDP), near Snowbird, Utah.
AIRCOA
The Autonomous Inexpensive Robust CO2 Analyzer measures CO2 concentrations at 3 levels on a tower, producing individual measurements every 2.5 minutes precise to 0.1 ppm CO2 and closely tied to the World Meteorological Organization (WMO) CO2 scale. A key component in the robustness of these analyzers is near real-time data processing with extensive automated diagnostic tests to verify normal operation and make new results available from a web interface every day. The success of the AIRCOA units has generated considerable outside interest, and the design has been shared with trained university (Pennsylvania State University, Oregon State University, Stanford University) collaborators installing similar systems around the U.S. NCAR researchers are also collaborating with member institutions of the CarboEurope project to deploy AIRCOA sensors at 5 sites in Europe. With support from the Earth Observing Laboratory (EOL) and the Director’s office, we have initiated a project in collaboration with a University of Colorado graduate student (Sherri Heck) to install AIRCOA units for CO2 measurements on the Navajo Reservation and in Africa, to provide carbon cycle insights, and to provide a basis for local education and capacity building.
Community Airborne Oxygen Instrument
The Community Airborne Oxygen Instrument has been developed. It is based on a vacuum-ultraviolet absorption technique. Because of the unique relationships between industrial, terrestrial, and oceanic exchange of carbon and oxygen, this instrument promises valuable insights into these processes.
MEDUSA
Multiple Enclosure Device for Unfractionated Sampling of Air has completed upgrades to and certification of a flask sampler in anticipation of participation in the Brazilian-Amazonia Regional Carbon Airborne (BARCA) study scheduled for this fall, as well as in future studies on the C130 and GV aircraft.
O2 / CO2 Calibration Facility
The Research Aviation Facility (RAF) of the EOL continues to support these efforts and RAF chemistry measurements by providing reference gases tied to internationally-recognized calibration scales. We have participated in two international round-robin cylinder comparison exercises in the past year, WMO (CO2) and GOLLUM (O2). Preliminary results show that our calibration system is performing very well in comparison to other participating laboratories. These instruments have also supported the work of two international visitors to NCAR.
Light-Aircraft Vertical CO2 Profiles
Analysis of light-aircraft vertical CO2 profiles measured at 12 global sites by 6 international laboratories. The results suggest a significant revision to the consensus view of the global carbon cycle by revealing systematic biases in atmospheric models that predict large northern terrestrial CO2 uptake and large tropical CO2 releases.
CO2 Transport in Complex Terrain
The difficulty in understanding the carbon dioxide (CO2) budget over complex terrain, and particularly its contribution to the global carbon balance, has led to two complementary field studies: the Carbon in the Mountain Experiment (CME) and the Airborne Carbon in the Mountain Experiment (ACME04). CME was an intensive ground-based field campaign over the foothills of the Colorado Front Range from 10 June to 5 October 2004. ACME was an airborne campaign conducted on a large-scale area of the Front Range from mid-May to the beginning of August, 2004. This unique combination allowed us to “scale” up the CO2 budget from several hundreds of meters to regional scales.
Nighttime-respired CO2 accumulated in North Park, Colorado, a bowl-shaped area surrounded by mountains. The disappearance of the accumulated high CO2 concentration in the morning due to the reverse of the slope flow and convective mixing was slower than expected. The CO2 concentration decreased exponentially with height even around 10 a.m. On the local scale, we found that at the Niwot Ridge CME site, the CO2 concentration increased with decreasing altitude. High CO2 was transported toward Como Creek, which runs along the main slope and is only about 2 m wide (Figure 1 - top). However the spatial variation of CO2 was also affected by the low respiration of CO2 from the cold water in Como Creek and local mixing generated by the thermal contrast between the creek and the surrounding land. As a result, the CO2 concentration was lower just over the water surface than it was over its banks (Figure 1 - bottom).
Future Work
For the future, NCAR is collaborating with investigators at University of Colorado, Colorado State University, and Harvard University to plan and conduct the ACME07 campaign on the University of Wyoming King Air. This campaign will be the second Airborne Carbon in the Mountains Campaign, focusing on Colorado and Wyoming, and will include flights from early spring through fall. The payload will include the RAF community oxygen instrument to be completed this fall. Two additional Rocky RACCOON sites will be added in the coming year in further support of NACP and will collaborate with Pennsylvania State University, Colorado State University, Oregon State University, and other institutions to formalize a national CO2 observing network and pursue improvements in inter-site comparability and data management. The MEDUSA sampler will participate in the BARCA campaign, collecting flasks using during 4 weeks of flights on a Brazilian Lear Jet over the Amazon, and analyzing the measurements made on these flasks at Scripps, NOAA/GMD, and CU INSTAAR. The Community Airborne Oxygen Instrument will be completed and tested as we pursue collaborations for its use on NSF aircraft. Five more AIRCOA samplers will be completed and deployed in the Netherlands, Germany, France (2), and Spain in collaboration with the CarboEurope project. We will continue our work on science and capacity building through the NCAR-CU Navajo and African CO2 measurement project. Continuing data analysis from both CME and ACME will focus on problems such as how topography affects CO2 transport differently during day and night, how this deviates from CO2 transport over flat terrain, and how regional and global terrestrial carbon budgets are affected. |
