The AmeriFlux Data Archive at the Carbon Dioxide Information Analysis Center offers several different product levels reflecting the data origin and level of processing, adjustment, and evaluation. The following lists and defines briefly the AmeriFlux product levels, most of which are available directly from this FTP area. For further details, please contact Tom Boden (bodenta@ornl.gov, 1 865 241 4842) Level 0 - Original/Raw Data ---------------------------- Original data (e.g., voltages from the data logger, measurements before processing into 30 min values) are not archived at CDIAC. Users interested in obtaining raw data need to contact the investigators at the individual AmeriFlux sites. Level 1 - Processed Data Provided by the Site Investigators ----------------------------------------------------------- These 30 min or 1 hr data are available here from the CDIAC anonymous area. Please note that the data files and documentation have not been standardized and remain in the original format submitted by the investigators. Some investigators provide gap-filled records. The data are organized by site. Please refer to the AmeriFlux fair-use data agreement (see ReadMe_First_AmeriFlux_Fair_Use_Policy.txt) before using these data. Level 2 - Data Checked & Formatted by CDIAC ------------------------------------------- CDIAC checks data received from individual sites and attempts to build a network-wide AmeriFlux database with consistent units, naming conventions, and reporting intervals. These data are available for graphing, querying, viewing, and downloading from a web-based interface (http://public.ornl.gov/ameriflux/data-access-select.shtml) requiring user registration. Data may be queried by site, measurement period, or parameter. CDIAC also offers standardized ASCII data files (derived from the same network-wide database described above) here from the CDIAC anonymous ftp server. These files contain core AmeriFlux measurements arranged by site, year, and whether the records contain gaps or not. These standardized files are intended to help satisfy data requirements for modeling and synthesis efforts. Level 3 - Processed Data With Quality Flags Assigned ---------------------------------------------------- AmeriFlux Level 2 standardized files are kindly processed by the European flux data activity to produce Level 3 and 4 files identical to the European regional network. Typically, Level 2 standardized files from the "with_gaps" subdirectory are used by the Europeans to produce the Level 3 and 4 data products, however, there are a few sites where "hybrid" files are provided. These "hybrid" files contain gap-filled meterological records and flux records containing gaps. Users will find a "hybrid" subdirectory only for those sites where the hybrid files were furnished to produce the Level 3 and 4 files. Level 3 files contain the same values as Level 2 files but with quality flags assigned and NEE calculated using standardized techniques. Level 4 - Gap-filled & Adjusted Data Files with GEP & Re Estimates ------------------------------------------------------------------ Level 4 files contain gap-filled (ANN and MDS techniques) and ustar filtered records, complete with calculated gross productivity and respiration terms. Flags with information regarding the quality of the original and gap-filled data are added. Select synthesis data sets, like the daily soil respiration data set compiled by Hibbard et al. (2005) for Northern Hemisphere sites, are available in the /synthesis-data subdirectory.