During August of 2000, COBRA conducted in-situ airborne measurements of CO₂, CO, H₂O, and meteorological parameters in the lower- and mid-troposphere over the U.S., exploring methods for quantifying terrestrial sources and sinks of CO₂ at regional and continental scales.  In addition, flask measurements of O₂/N₂ (Scripps) and CH₄, N₂O, SF₆, d¹³C (NOAA CMDL) were conducted.
 

The COBRA airborne platform is the University of North Dakota Cessna Citation II, a straight-wing twin-engine fanjet  suited for intensive vertical profiling of the entire atmosphere including the PBL (planetary boundary layer). The flight duration of 3.5~4 hours allows coverage of continental scales. In addition to the science payload, the plane carries two pilots and two science crew.

In COBRA-2000, flights originated at Grand Forks, ND, the home base for the UND Citation II.  A Lagrangian experiment was performed first, in Southern Manitoba and North Dakota.  After a transit to Centennial Airport near Denver, a day was spent surveying through Wyoming and Idaho.  Then a transit (Southern tier survey) was executed from Denver to Boston (Hanscom Field), with numerous dips and stops.  Next two days of regional flying were conducted over Maine. Finally a survey was made across the Northern Tier states back to Grand Forks, ending with regional Lagrangian flights over the tall tower at WLEF.

Lagrangian Regional-scale Experiment :
Airmass-following (Lagrangian) experiments possess the potential for minimizing the advection term in the budget.  We tested this Lagrangian approach in COBRA-2000 by conducting several flights sampling an air mass for 12 - 24 hours.  We developed and used STILT model to simulate the motions of tracer particles backwards in time and used it to follow an airmass through a 24hour period.

Large-scale Surveys :
 Two large-scale, trans-continental surveys were conducted in COBRA-2000.  The sampling strategy generated cross-sections showing distinct fingerprints of influences at the continental scale. Moreover, results show how signatures of underlying sources and sinks are clearly observable in the atmosphere using aircraft sampling.