The North American Carbon Program Plan (NACP)
A Report of the Committee of the
U.S. Carbon Cycle Science Steering Group

Chapter 3: Synergy of the NACP with Other Major Areas of Research

 Atmospheric Chemistry

The intensive field programs and long-term measurements of the NACP offer unique opportunities for joint research with atmospheric chemistry programs at NASA, NSF, NOAA, and DOE. Trans-oceanic and trans-continental transport and transformation of pollutants are among the most important issues of current interest in atmospheric chemistry. Major airborne field programs are currently under discussion for North America in the time frame being considered for NACP IOPs. The synergy between the NACP and atmospheric chemistry programs is evidently bi-directional, with potent benefits flowing in both directions.

Intensive Field Campaigns with Atmospheric Chemistry

Consideration of potential experiments suggests that joint missions between the NACP and atmospheric chemistry programs would offer major advantages, providing enriched data sets with very few tradeoffs. The NACP focus on long-lived tracers, exchange processes between the PBL and the free troposphere, and partitioning of sources and sinks between forests, agriculture, and industry, provides key information for studies of pollutants that travel long distances in the atmosphere. The enormously sophisticated instrument payloads for chemical measurements on heavy-lift payloads (DC-8, C-130, P-3) provide extremely powerful multi-tracer constraints for source/sink attribution, as well as data to help define the magnitude of complications such as in situ production of CO from labile hydrocarbons or long-range transport of concentration anomalies for CO2, CH4, or CO in the upper troposphere.

The NACP plan therefore envisions that the intensives will be carried out in close collaboration with atmospheric chemistry programs and the associated airborne measurement missions.

Long-Term Airborne and Surface Measurements with Atmospheric Chemistry

The NACP plan calls for frequent (1 to 2 day interval), continuing measurements of atmospheric composition using a limited number (2-4) of small jet aircraft, intended to provide critical complements to the soundings by light aircraft. These jet aircraft platforms will transit coastal regions, higher altitudes, and other areas inaccessible to light aircraft. Their payloads can potentially include a wide range of chemistry measurements, including radicals (NOX, possibly OH), nonmethane hydrocarbons, aerosol composition, and others. A number of possibilities have been discussed for developing small, rugged sensors that could be used for this type of work, and development activities are under way.

Data provided by these aircraft will not only aid the NACP, but could revolutionize understanding of atmospheric chemistry over North America. Currently, data are collected routinely mainly at sites in polluted areas, and aircraft data are limited to a rather small number of campaign-style missions, also usually in polluted areas. The new data will provide insight into background conditions and long-range transport not hitherto available.

Measurements of reactive chemicals and aerosols at ground stations provide complementarity and will be undertaken at a similarly selected, limited subset of the ground stations (tall towers and flux towers).

The NACP plan envisions a small number of jet aircraft in the long-term measurement program operated jointly with atmospheric chemistry programs and equipped with sensors for key reactive species and aerosols.

 Resource Management and Ecological Sciences

The NACP has strong synergy with resource management (forests, agriculture) and ecological research programs, primarily in two ways. The benefits are evidently bi-directional, as for chemistry.

Long-Term Measurements and Emergent Properties of Ecosystems

The carbon budget of a region represents an integral emergent property of the ecosystems there on a large scale. For land managers, this means, for example, that the actual accumulation of fuel on fire-prone lands can be measured. The carbon budget for the growing season in the Corn Belt tells managers in near-real-time the growth trajectory of the crop, complementing conventional measures such as NDVI.

Transient Responses to Environmental Forcing

Seasonally resolved rates for net uptake or release of CO2 from agricultural and forest ecosystems provide unique, quantitative indicators for processes and net productivity at the landscape scale. NACP measurements in the long-term network and IOPs, and calibrated, near-real-time ecosystem models for vegetation will measure the effects of climatic variations on ecosystem net growth with time resolution sufficient to resolve major shifts as they are occurring.

The NACP plan envisions close coordination between carbon cycle science and resource management and ecological programs, with joint consideration of measurement and modeling issues to maximize two-way synergy.

 Weather Forecasting and Climate

There is a critical synergy between NACP efforts and weather and climate studies. Flux tower data and biophysical model analyses, available in near-real-time, provide improved constraints on latent and sensible heat fluxes, roughness lengths, and other properties. Currently, surface flux data have no direct impact on weather forecasts, because the data are not available for assimilation, and assimilation frameworks do not exist. The development of these data sets and associated diagnostic models incorporating remotely sensed forcings promises significant benefits for weather forecasting.

The potential for CO2 concentrations and fluxes to benefit meteorological forecasts and analysis has been recognized at the ECMWF, which already has research under way to enable simulation of CO2 distributions in the atmosphere; once the data are available, forecasts will use variations to correct satellite-derived temperatures. More sophisticated applications are also envisioned. Tracer distributions are very sensitive to the details of atmospheric advection, and assimilation of tracer observations could help improve forecasts by improving representation of boundary-layer processes. ECMWF has in place plans to assimilate CO2 data with this objective in mind. Additional synergies involving, for example, CO data deserve exploration.

The program envisions close collaboration with operational centers to enable NACP tracer data to be utilized to improve operational weather forecasting. Parallel applications to help improve climate models are a high priority for developments in surface-atmosphere models for CO2 sources and sinks.

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