Date: Thu, 13 Sep 2001 17:04:49 -0600 From: Britt Stephens Reply-To: bstephens@cmdl.noaa.gov Organization: NOAA /CMDL To: nacp@python.as.harvard.edu, nacp@io.harvard.edu Subject: NACP comments Hi Steve, I haven't had time to do a thorough read of the draft, but wanted to pass on a few quick comments: Page 5, bullet 1: "increasingly accurate . . . regional" may be an inappropriate characterization as they currently are very inaccurate on even continental scales. Page 6, relationship to LSCOP: you should read the final version of LSCOP. As it became apparent that the funding situation for NACP-like work might be very different than our earlier assumptions, we change the atmospheric recommendations quite a bit. The relationship now is much tighter than implied by your "complementing . . . LSCOP" statement. I have copied the relavent recommendations below, so you don't have to go to the web. Page 8-9, integrating observations: do you want to list improved boundary-layer parameterizations and higher-resolution models that can use high-frequency data here? Page 9, emphasis on N.A.: you might also point out the heightened interest in N.A. sources because of the Fan study, and the extensive existing datasets for land use/characterization as further motivators for focusing on N.A. Page 10, report: You should cite LSCOP here, as a whole chapter was devoted to such a report. Best of luck with the revisions, Britt Priority Level 2: Make intensive and extensive measurements of the vertical distribution of CO2 over continents. 2.a. Conduct intensive CO2 measurements to elucidate the North American carbon cycle through a combination of airborne, tower, and ground and ship-based measurements. The purpose of these intensive measurements is to learn how to best measure fluxes on regional scales with an ongoing program, to demonstrate this capability, and to develop the infrastructure to leave in place for a long-term North American observational system. These measurements will address the crucial question of how to scale up from local source estimates, through landscape, regional, and continental to global scales by observing the development and propagation of terrestrial, industrial, and oceanic signals across the continent. They will guide the location of long-term observations such as aircraft profiles and tall towers, and will allow the investigation of potential gaps and sampling biases in these observations such as those due to diurnal, fair-weather, continental, or low-altitude sampling. These intensive campaigns will also provide a wealth of data for testing and improving the next generation of coupled carbon cycle models, which in turn will be able to use these data for network design purposes. Cost estimate: Approximately $10,000,000 for a month-long campaign (of which $2,000,000 is for aircraft time and rental). CCSP: Program elements 2 and 6. 2.b. Repeated vertical profiles by aircraft sampling over continents. In addition to the intensive measurements, ongoing observations of continental CO2 distributions will be required. The temporal coverage of the intensive measurements will be limited, and many important processes, such as the seasonal rectifier effect, only manifest themselves on longer time scales. Over North America, these measurements must be at a high enough resolution to provide a context for more intensive measurements and to answer the question of how many and what type of continental observations are required for our ongoing network. For these purposes, synoptic-scale coverage of around 25 sites over North America with a sampling frequency of every 2 days is appropriate. This resolution will only be possible using the analyzer recommended in 1.b., but a subset of the flights should include flask samples for purposes of quality control and for measurement of additional tracers. For continental regions other than North America, a few profiling sites will greatly improve the quality of global inverse calculations. At least two aircraft sampling locations over South America, and one each over Africa, and Eastern and Western Russia are required to fill the largest gaps in global coverage. Aircraft profiles will also be critical for validating future satellite CO2 systems and ground-based spectrometers, both of which have significant promise for measuring column CO2 as well as significant potential biases. It would also be highly advantageous to include measurements of CO as a pollution tracer on these flights, if a robust analyzer becomes available (see recommendation 3.e.). Cost estimate: One-time setup costs, $3,000,000 (includes flask units and laboratory instruments); operational costs, $7,000,000 per year (of which $4,000,000 is for aircraft rental). CCSP: Program elements 2 and 3. 2.c. Tall tower observations. Aircraft and satellite measurements may suffer from diurnal or fair-weather sampling biases. Continuously operating tall towers can provide critical data at night and in bad weather, and extensive data sets for investigating the interaction between CO2 fluxes and boundary layer mixing. Species other than CO2, such as CO (see recommendation 3.e.), should be measured for air mass characterization, which will allow an ongoing assessment of sources and sinks over hundreds of kilometers surrounding the tower. A few towers, such as the WLEF tower in Wisconsin, should be selected for a more intensive program involving flux measurements and studies addressing boundary layer mixing, with a full complement of meteorological observations. All of these high-intensity towers will be located in North America, to improve our estimates of temperate North American CO2 exchange and to leverage numerous other investigations and resources. It is anticipated that investigators in other countries will initiate additional tall tower programs. Vertical extrapolation methods (Potosnak et al., 1999; the "virtual tall tower" concept, K. Davis) should also be pursued as a possible means of obtaining additional information on continental background concentrations. Cost estimate: One-time setup for 12 towers, $2,300,000; operational costs, $800,000 per year. CCSP: Program Element 3. -- Britton B. Stephens Cooperative Institute for Research in Environmental Sciences University of Colorado Campus Box 216 Boulder, CO 80309-0216 NOAA Climate Monitoring and Diagnostics Laboratory Mail Code R/CMDL1 325 Broadway Boulder, CO 80305 (303)497-6999 (office) (303)497-5590 (fax) bstephens@cmdl.noaa.gov (email)