FLUXNET-CH4 is an initiative led by the Global Carbon Project, in close partnership with AmeriFlux and EuroFlux, to compile a global database of eddy covariance (EC) methane flux measurements. Data are standardized, post-processed (i.e., partitioned and gap-filled), and released as FLUXNET-CH4 (Delwiche et al. 2021, Knox et al. 2019). FLUXNET-CH4 Version 1.0 includes data from 81 sites, representing freshwater, coastal, upland, natural, and managed ecosystems. The near continuous, high-frequency nature of EC measurements offers significant promise for improving our understanding of ecosystem-scale CH4 flux dynamics. FLUXNET-CH4 exists thanks to the hard work of the site teams who collected these data and their willingness to participate in the FLUXNET-CH4 effort. Please refer to the Data Policy page for data usage and acknowledgement requirements. Funding for the FLUXNET-CH4 initiative was provided by the Gordon and Betty Moore Foundation and the USGS Powell Center.
A detailed description of the FLUXNET-CH4 Community Product is available in Delwiche et al. 2021, co-authored by data teams and members of all site teams contributing to FLUXNET-CH4.
The FLUXNET-CH4 Community Product is distributed under the two tiers of the FLUXNET2015 Data Policy. Tower teams chose data policy tiers for their site. Data distributed in both tiers can be accessed from the Data Download page for the FLUXNET-CH4 Dataset. To see a list of site-years of data available for each site, please refer to the list of sites and data availability.
IMPORTANT: In case of a synthesis using both CC-By-4.0 (Tier One) and Tier Two data, all data should be treated as Tier Two.
Temporal aggregation resolutions
The FLUXNET-CH4 Community Product provides data in two standard temporal aggregations. Tower teams generate either half-hourly (HH) or hourly (HR) data sets, depending on the conditions in the site. Half-hourly data are the basis of all the processing done for this dataset and are the finest grained temporal resolution provided. FLUXNET-CH4 also contains daily (DD) aggregations.
The FLUXNET-CH4 Community Product includes a file containing select metadata for each site, including site personnel, location, climate and biome classification, among others. Additionally, each site has 6 metadata columns related to site vegetation. The FLUXNET-CH4 sites were assigned vegetation classifications using a 1) presence/absence, designated by Avni Malhotra based on site literature and 2) dominant vegetation based on a questionnaire sent to lead site investigators. For both presence/absence and dominant vegetation, the following plant functional types (PFTs) were considered: brown mosses, Sphagnum mosses, ericaceous shrubs, aerenchymatous plants, and trees. See Delwiche et al. 2021 methods for a detailed description.
- SITE_ID: Site identification code as assigned by regional flux data network
- SITE_NAME: Site name determined by site personnel
- SITE_PERSONNEL: Person(s) primarily responsible for data collection of FLUXNET-CH4 V1.0 data (may be different than current site PI information, which can be found under individual site information pages)
- COUNTRY: Site country
- LAT: Latitude
- LON: Longitude
- SITE_CLASSIFICATION: Site classifications were designated based on literature description of sites and designations were made from the following categories (See Delwiche et al. 2021 for details, designations were made by Kyle B. Delwiche and Gavin McNicol).
- Salt marsh
- Wet tundra
- Drained (former wetlands that have been artificially drained)
- Alpine meadow
- Crop (crop type)
- Mixed forest
- Needleleaf forest
The FLUXNET-CH4 Community Product is distributed in files separated by sites and by temporal aggregation resolutions (e.g., half-hourly or daily). Version information is also assigned to the file to document changes required for a site. The file naming convention below details these options for each file. Multiple files with different temporal aggregation resolution (same site, same data product) are available for download as a single ZIP file archive. Site information metadata are also provided with a data download. Data variable descriptions can be found here.
- PUBLISHER: 3-character code for publisher. Possible options:
- FLX: FLUXNET data product
- other codes can be used by publishers (e.g. regional networks) when distributing data from their databases
- HH: Half-Hourly time steps
- HR: Hourly time steps (NOTE: documentation for HH also applies to HR)
- DD: Daily time steps
- csv: Comma-separated values in a text file (ASCII)
- zip: Archive file with all temporal resolutions for same site and data product
Time zone convention
Time is reported in local standard time (i.e., without “Daylight Saving Time”). The timezone information (with respect to UTC time) is reported in the site metadata.
For text file data representations (i.e., CSV formatted), the variable/column order is relevant. The order of columns will NOT be guaranteed to be the same for different files (e.g., different sites), even though they will be similar in many cases. This means that any data processing routines should rely on the variable name (which is always consistent) and not the order of occurrence of that variable in the file. Timestamps are the only exception and will always be the first variable(s)/column(s) of the data file.
Missing data values are indicated with -9999 (without decimal points) as a replacement value, independent of the cause for the missing value.
Please send questions, comments, and feedback to [email protected]. We’d love to hear from you!
Please use the Data Downloads page to get access to the FLUXNET-CH4 Community Product.
Delwiche et al., 2021. “FLUXNET-CH4: A global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands.” Earth System Science Data Discuss https://doi.org/10.5194/essd-2020-307.
Knox, Sara H., Robert B. Jackson, Benjamin Poulter, Gavin McNicol, Etienne Fluet-Chouinard, Zhen Zhang, Gustaf Hugelius, et al. 2019. “FLUXNET-CH4 Synthesis Activity: Objectives, Observations, and Future Directions.” Bulletin of the American Meteorological Society 100 (12): 2607–32.