1. 1 - What are the local, regional, and continental-scale exchanges of carbon, nitrogen, and reactive species? What are their relationships to underlying ecosystem parameters and processes? How are they responding to environmental, climatic, atmospheric-chemistry, and land-use perturbations? 2 - How can we measure terrestrial exchange of CO 2 and other greenhouse gases on the time and space scales required to support domestic carbon management efforts and international climate treaties? 3 - How do coupling between carbon, nitrogen, iron, and sulfur cycling and associated non-linear feedbacks affect climate, air quality, and ecosystem function on local to global scales? 4 – What is the influence of mineral aerosols on other biogeochemical cycles? How are they transported from the continents and how are these processes changing? Biogeosciences What are the priority questions that can be addressed through observations?

2. Biogeosciences What observations should ATD be doing to address these scientific drivers? Airborne: Instrumentation for fast-response, precise, and accurate measurements of CO 2, CO, H 2 O, O 3, O 2 /N 2, CO 2 isotopes, radon, and photochemically active species. A flask system or systems for collection of discrete, dried, unfractionated samples for laboratory analyses of these and other gases or isotopes. Instrumentation for eddy flux measurements of CO 2, CO, O 3, and H 2 O. Disjunct eddy accumulator to enable flux measurements of a wide range of compounds. Remote sensing instrumentation, including hyperspectral imaging, CO 2 LIDAR, microwave soil moisture, and accurate surface IR temperature imaging. Ground based: Tower based eddy flux measurements for CO 2, H 2 O, and energy. Medium arrays of towers (10-20) and instruments for concentration of CO 2 and other species. Large (100-1000) arrays of intelligent sensors for high variability environmental parameters. Advanced tethered balloon instrumentation for multi-species boundary layer profiles. Enclosure techniques for measuring soil and plant exchange of CO 2 and reactive species.

3. Strategic Partnerships: Many BGS measurements require a high level of specific expertise. New mechanisms may be necessary to allow for and encourage support of community instrumentation by non-ATD scientists and technicians. Examples could include instrumentation for reactive nitrogen species supported by ACD and HIAPER MREFC developments supported by a university. Long-term monitoring: Many BGS questions can only be addressed by measurements in all seasons or for multiple years. This will require relatively autonomous instrumentation and a capacity to support regular annual cycle length campaigns. In the case of longer deployments, technology transfer from ATD to universities may be the preferred means of support. Advanced calibration: Many BGS measurements require high levels of precision and accuracy that can only be achieved through rigorous calibration procedures, including for example the maintenance and propagation of calibration scales based on suites of high-pressure gas cylinders. Training: The BGS community has relatively less experience utilizing ATD facilities and less infrastructure for advanced instrument development and airborne science. NCAR should partner with universities and agencies to entrain BGS students and postdocs into earth system observing technique development, and provide internship and summer opportunities and curricular material. Biogeosciences What will be required to accomplish these efforts?