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Description
The Level-4 (L4) carbon product (SPL4CMDL) provides global gridded daily estimates of net ecosystem carbon (CO2) exchange derived using a satellite data based terrestrial carbon flux model informed by the following: Soil Moisture Active Passive (SMAP) L-band microwave observations, land cover and vegetation inputs from the Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), and the Goddard Earth Observing System Model, Version 5 (GEOS-5) land model assimilation system. Parameters are computed using an Earth-fixed, global cylindrical 9 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0) projection.
Version Description
Changes to this version largely affect model inputs and ancillary files rather than changes to the internal model structure or code. Note that Version 4 is slightly better than Version 3 in RMSE terms, with improvement generally larger for drier sites. Specific changes include:
The carbon model biome properties lookup table (BPLUT) has been calibrated using an augmented FLUXNET global tower site record which includes more calibration sites (335 sites compared to 228 sites for V3), expanded tower data records extending to at least 2015, and the addition of new tower sites representing more land cover types.
Revised Level-4 carbon global model calibration and SOC initialization using an extended (2000-2017) MODIS fPAR (V006) record and the latest SMAP Nature Run (NRv7.2) climate data records.
Implemented minor changes to spatial weighting of calibration tower sites within a model grid cell and reduced the outlier influence on model response curve fitting.
Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.
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Kimball, J., Jones, L., Endsley, A., Kundig, T., & Reichle, R. (2018). SMAP L4 Global Daily 9 km EASE-Grid Carbon Net Ecosystem Exchange, Version 4 [Data set]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/9831N0JGVAF6 Date Accessed: 2026-06-17
Kimball, John, Lucas Jones, Arthur Endsley, Tobias Kundig, and Rolf Reichle. “SMAP L4 Global Daily 9 Km EASE-Grid Carbon Net Ecosystem Exchange, Version 4.” NASA National Snow and Ice Data Center Distributed Active Archive Center, 2018. doi:10.5067/9831N0JGVAF6. Date Accessed: 2026-06-17
Kimball, John, et al. SMAP L4 Global Daily 9 Km EASE-Grid Carbon Net Ecosystem Exchange, Version 4. NASA National Snow and Ice Data Center Distributed Active Archive Center, 2018, doi:10.5067/9831N0JGVAF6. Date Accessed: 2026-06-17
Zolkos, Scott, Tank, Suzanne E., Kokelj, Steven V., Striegl, Robert G., Shakil, Sarah, Voigt, Carolina, Sonnentag, Oliver, Quinton, William L., Schuur, Edward A. G., Zona, Donatella, Lafleur, Peter M., Sullivan, Ryan C., Ueyama, Masahito, Billesbach, David, Cook, David, Humphreys, Elyn R., Marsh, Philip