------------------------------------------------------------ Readme file to accompany COBRA 2003 continuous aircraft data ------------------------------------------------------------ TERMS AND CONDITIONS (Adapted from NOAA and NACP data policy) ------------------------------------------------------------ CITATION INFORMATION Use of these data in any part implies an agreement on the part of the user that individuals and/or institutions responsible for contributing to data sets used must be specifically cited in addition to a general citation of the NACP greenhouse gas database. The COBRA 2003 continuous aircraft data set should be cited as follows: 1) Hurst, D. F., J. C. Lin, P. A. Romashkin, B. C. Daube, C. Gerbig, D. M.Matross, S. C. Wofsy, B. D. Hall, and J. W. Elkins(2006), Continuing global significance of emissions of Montreal Protocol ~V restricted halocarbons in the United States and Canada,J. Geophys. Res., 111, D15302, doi:10.1029/2005JD006785. 2) Kort, E. A., J. Eluszkiewicz, B. B. Stephens, J. B. Miller, C. Gerbig, T. Nehrkorn, B. C. Daube, J. O. Kaplan, S. Houweling, and S. C. Wofsy (2008), Emissions of CH4 and N2O over the United States and Canada based on a receptor-oriented modeling framework and COBRA-NA atmospheric observations, Geophys. Res. Lett., 35, L18808, doi:10.1029/2008GL034031. 3) Miller, S. M., D. M. Matross, A. E. Andrews, D. B. Millet, M. Longo, E. W. Gottlieb, A. I. Hirsch, C. Gerbig, J. C. Lin, B. C. Daube, R. C. Hudman, P. L. S. Dias, V. Y. Chow, and S. C. Wofsy, Sources of carbon monoxide and formaldehyde in North America determined from high-resolution atmospheric data, Atmos. Chem. Phys. Discuss., 8, 11395-11451, 2008. NACP investigators will include an acknowledgement in each publication or presentation arising from participation in NACP. The wording shall be similar to the following: "This study was part of the North American Carbon Program." Data providers and funding agencies may request additional acknowledgements. Upon publication of results, investigators should send the NACP Office an electronic copy of the publication. USE OF DATA These data are made freely available to the public and the scientific community in the belief that their wide dissemination will lead to a greater understanding and new scientific insights. The availability of these data does not constitute publication of the data. We rely on the ethics and integrity of the user to assure that the source(s) receive fair credit for their work. If the data are obtained for potential use in a publication or presentation, the source(s) should be informed at the outset of the nature of this work. If the source's data are essential to the work, or if an important result or conclusion depends on their data, co-authorship may be appropriate. This should be discussed at an early stage in the work. Manuscripts using the source's data should be sent to the source(s) for review before they are submitted for publication so we can ensure that the quality and limitations of the data are accurately represented. RECIPROCITY AGREEMENT Use of these data implies an agreement to reciprocate. Laboratories making similar measurements agree to make their own data available to the general public and to the scientific community in an equally complete and easily accessible form. Modelers are encouraged to make available to the community, upon request, their own tools used in the interpretation of the source data, namely well documented model code, transport fields, and additional information necessary for other scientists to repeat the work and to run modified versions. Model availability includes collaborative support for new users of the models. COBRA 2003 PROJECT PURPOSE & DESCRIPTION ---------------------------------------- The program was coordinated with the Fluxnet Canada Research Network (FCRN) and Environment Canada. The PIs for the project are: Steven C. Wofsy, Harvard University, swofsy@fas.harvard.edu James W. Elkins, NOAA, James.W.Elkins@noaa.gov Britton B. Stephens, NCAR/UCAR , stephens@ucar.edu John B. Miller, NOAA, John.B.Miller@noaa.gov The Terrestrial Ecology Program (director, Dr. Diane E. Wickland) of NASA's Earth Science Enterprise provided the principal funding for this airborne campaign, with additional resources from NOAA-CMDL and NOAA-OGP, NASA's Upper Atmosphere program, and from NSF (Atmospheric Chemistry Program and NCAR). The objective of COBRA 2003 is to test concepts for observations and data assimilation to determine the large scale sources and sinks of greenhouse gases and ozone-destroying gases from North America. The study will cover spatial scales from regional to continental. Gases of interest include CO2, CO, CH4, N2O, chlorofluorcarbons (CFCs), chlorinated solvents (CH3CCl3, CCl4 ), SF6, ozone (O3), and molecular hydrogen (H2). The capability to measure current and future sources and sinks of greenhouse gases and ozone-destroying chemicals represents a challenging scientific problem with important societal consequences. In order to predict future climate forcing and to project reocovery of stratospheric ozone from current levels of depletion, we must be able to determine the location and magnitude of emissions and understand them. But current models that simulate emissions of greenhouse gases do not represent current observations of concentrations across latitudes or vertical profiles of these gases within a factor of two. Transport of these gases into the middle and upper atmosphere is uncertain because convection, land ocean exchange, and other atmospheric processes are very difficult to model. The thickness of the atmospheric boundary layer decreases from daytime to nighttime, and transport processes also change seasonally. Diurnal and seasonal variations of atmospheric dynamics are correlated with variation of surface emissions, especially for CO2, making observations of trace gases very difficult to interpret. Previous studies have pointed out a large terrestrial sink for CO2 exists in North America. Systematic vertical profile data of the trace gases between 30 and 10,000 meters are required to critically test the models used in these analyses. A series of atmospheric experiments called the CO2 Budget and Regional Airborne Study with recent emphasis on North America (COBRA-NA 2003) is intended to take first steps in this direction. The experiment is anchored upon the extensive ground-based data from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) Cooperative Station Networks for carbon cycle and halocarbon trace gases. The experiment will focus also on the extensive emission data at Harvard Forest, Massachusetts over the past 10 years by flying across the pollution plume from the New York City and Washington, D. C. metropolitan corridor. The intention is to estimate emissions using a data assimilation approach as well as by using a carbon monoxide (CO) as a reference for emission strength combined with the trace gas-CO correlations observed in COBRA-2003. This experiment is a continuation of an earlier COBRA experiment over a more limited region of North America in 2000. In that study significant deficiencies were discovered in the resolution and mass conservation properties of many existing data sets for analyzed meteorological fields. These issues currently limit the capability to accommodate the high degree of variability of local CO2 emissions (patchiness) and to use the information about sources contained in observed atmospheric variations. The current measurements will be analyzed using the advanced regional-scale meteorological model from scientists at the University of Sao Paulo (Brazil), who will collaborate with the team to apply their BRAMS model (Brazilian development of the Regional Atmospheric Mesoscale Modeling System (RAMS) model) for atmospheric dynamics to address the deficiencies of current meteorological models. The aircraft platform used in COBRA-NA 2003 is the University of North Dakota Cessna Citation II, a modified executive jet for atmospheric research (see picture above). The airborne experiment consists of a racetrack from Boulder to the west coast of the United States (Eureka, California) North to Campbell River British Columbia, across Canada to the east coast of North America (Yarmouth, NS), south to Portsmouth, NH, and back to Boulder (see map). Vertical profiles have been acquired over NOAA/CMDL cooperative stations located at Niwot Ridge, Colorado, Moody, Texas, Trinidad Head, and Harvard Forest. Other NOAA/CMDL stations and AmeriFlux and Fluxnet Canada sites along and outside the racetrack will provide important data on the boundary conditions for the flow of air through the area of the racetrack and for surface exchange fluxes. There have also been also excursions over the Pacific Ocean from California, and the Atlantic Ocean from Pease, New Hampshire to Sable Island to examine coastal influence of marine air and the mixing processes between maritime and continental air, and intensive regional flights in Oklahoma and New England. The two bases of operations will be one at the Jefferson County Airport (Jeffco) in Broomfield, Colorado, and the other at Pease (Portsmouth), New Hampshire. Test flights started on May 22, 2003 at Jeffco Airport and the first racetrack started there on May 26. The second racetrack started from Jeffco on June 19 and until June 28. Measurements of CO2, CO, H2O, aerosol size and concentration were measured at 1 Hz on the aircraft by scientists from Harvard University and University of North Dakota. Scientists from the Halocarbons and other Atmospheric Trace Species Group (HATS) group in NOAA/CMDL operated an in situ gas chromatograph (GC) . The HATS airborne GC, Airborne Chromatograph for Atmospheric Trace Species (ACATS-IV), measures twelve different trace gases: nitrous oxide (N2O), SF6, CFC-12 (CCl2F2), and halon-1211 (CBrClF2), once every 70 seconds; and hydrogen (H2), CO, methane (CH4), CFC-11 (CCl3F), CFC-113 (CClF2-CCl2F), chloroform (CHCl3), methyl chloroform (CH3CCl3), and carbon tetrachloride (CCl4) once every 140 seconds. A whole air sampler (WAS) for flasks was operated by researchers from the Cooperative Institute for Research in the Environmental Sciences (Univ. of Colorado), the National Center for Atmospheric Research, and Scripps Institution for Oceanography. The WAS collects air in glass flasks to be measured for a suite of trace gases at Scripps, NOAA/CMDL, and CU/INSTAAR. These include CO2, CO, H2, CH4, N2O, and SF6 concentrations, and ratios of O2/N2, Ar/N2, and isotopic C13/C12 and O18/O16 in CO2, and C13/C12 in CH4. VARIABLE NAMES -------------- YYYYMMDD : Year, month, and day of sampling. Data from 20030523 and 20030525 is from test flights. doy : Absolute day of year UTC : Coordinated Universal Time, in seconds from midnight flt.num : Flight number, ranges between 1 and 3 profile.num : Daily vertical profile number, ranges from 1 to 18. latitude : Latitude, in degrees longitude : Longitude, in degrees altitude : Altitude from POS, in meters press.altitude : Pressure altitude, in meters rad.altitude : Radar altitude, in meters airT.C : Air temperature, in degrees celsius dew.pt_EGG : Dew point from EG&G, in degrees celsius dew.pt_TDL : Dew point from TDL (Laser Hygrometer), in degrees celsius frost.pt_TDL : Frost point from TDL (Laser Hygrometer), in degrees celsius THETA : Potential temperature, in Kelvin THETAe : Equivalent potential temperature, in Kelvin static.press : Static pressure, in mbar cabin.press : Cabin pressure, in mbar ground.speed : Aircraft ground speed from POS, in m/s wind.u : u-component of wind vector (positive North, negative South) wind.v : v-component of wind vector (positive East, negative West) CCl4_ACATS : Carbon tetrachloride mixing ratio from ACATS-IV, in ppt SD.CCl4_ACATS : Carbon tetrachloride uncertainty 1-sd, in ppt cfc11_ACATS : Trichlorofluoromethane (CFC) mixing ratio from ACATS-IV, in ppt SD.cfc11_ACATS : Trichlorofluoromethane uncertainty 1-sd, in ppt cfc113_ACATS : 1,1,2-Trichloro-1,2,2-trifluoroethane (CFC) mixing ratio from ACATS-IV, in ppt SD.cfc113_ACATS : 1,1,2-Trichloro-1,2,2-trifluoroethane uncertainty 1-sd, in ppt cfc12_ACATS : Dichlorodifluoromethane (CFC) mixing ratio from ACATS-IV, in ppt SD.cfc12_ACATS : Dichlorodifluoromethane uncertainty 1-sd, in ppt CHCl3_ACATS : Trichloromethane (chloroform) mixing ratio from ACATS-IV, in ppt SD.CHCl3_ACATS : Trichloromethane uncertainty 1-sd, in ppt CH3CCl3_ACATS : 1,1,1-Trichloroethane (methyl chloroform) mixing ratio from ACATS-IV, in ppt SD.CH3CCl3_ACATS: 1,1,1-Trichloroethane uncertainty 1-sd, in ppt CH4_ACATS : Methane mixing ratio from ACATS-IV, in ppb SD.CH4_ACATS : Methane uncertainty 1-sd, in ppb CO_ACATS : Carbon monoxide mixing ratio from ACATS-IV, in ppb SD.CO_ACATS : Carbon monoxide uncertainty 1-sd, in ppb CO_VUV : Carbon monoxide mixing ratio from Harvard VUV, in ppb COVUV.10sec : Carbon monoxide mixing ratio from Harvard VUV, time averaged over 10 seconds (moving block average), in ppb CO2_LICOR : Carbon dioxide mixing ratio from Harvard CO2 instrument, in ppm H1211_ACATS : Bromochlorodifluoromethane (Halon 1211) mixing ratio from ACATS-IV, in ppt SD.H1211_ACATS : Bromochlorodifluoromethane uncertainty 1-sd, in ppt H2_ACATS : Hydrogen mixing ratio from ACATS-IV, in ppb SD.H2_ACATS : Hydrogen uncertainty 1-sd, in ppb H2O_EGG : Water vapor mixing ratio from EG&G, in g/kg H2O_TDL : Water vapor mixing ratio from TDL (Laser Hygrometer), in ppmw N2O_ACATS : Nitrous oxide mixing ratio from ACATS-IV, in ppb SD.N2O_ACATS : Nitrous oxide uncertainty 1-sd, in ppb O3_2B : Ozone mixing ratio from 2B monitor, in ppb SF6_ACATS : Sulfur hexafluoride mixing ratio, in ppt SD.SF6_ACATS : Sulfur hexafluoride uncertainty 1-sd, in ppt MISSING VALUES -------------- For files in .RData format, missing values are represented by "NA". For files in .csv format, missing values are represented by "NaN"