Observation Instance

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{
    "ob_id": 43388,
    "uuid": "375ffdb8f0a445e380b4b9548655f5f9",
    "title": "ESA Snow Climate Change Initiative (Snow_cci): Daily global Snow Cover Fraction - snow on ground (SCFG) from MODIS (2000-2023), version 4.0",
    "abstract": "This dataset provides daily Snow Cover Fraction on Ground (SCFG) derived from Terra MODIS observations, produced within the ESA Climate Change Initiative Snow project.\r\n\r\nSCFG expresses the proportion of land area within each about 1 km x 1 km pixel that is covered by snow. In forested areas, the masking effect of the forest canopy is corrected to estimate the SCFG. The SCFG is given in percentage (%) per pixel.\r\n\r\nThe SCFG product is available at about 1 km pixel size for global land areas except the Antarctica and Greenland ice sheets and permanent snow and ice areas. The coastal zones of Greenland are included. The SCFG time series spans 24 February 2000 to 31 December 2023.\r\n\r\nThe SCFG product is based on Moderate resolution Imaging Spectroradiometer (MODIS) data on-board the Terra satellite. For the SCFG product generation from MODIS, multiple reflective and emissive spectral bands are used. In a first step, clouds are masked using an adapted version of the Simple Cloud Detection Algorithm (SCDA) (Metsämäki et al., 2015).  For all remaining pixels, the snow_cci SCFG retrieval method is applied, using spectral bands centred at about 0.55 µm and 1.6 µm, and an emissive band centred at about 11 µm. The snow_cci snow cover mapping algorithm is a two-step approach that first identifies pixels which are assessed as snow free, followed by SCFG retrieval for remaining pixels. \r\nPermanent snow/ice and water bodies are masked using the Land Cover CCI 2000 dataset, supplemented by a manually mapped salt-lake mask.  Per-pixel uncertainty is provided in the ancillary variable as an unbiased Root Mean Square Error (RMSE) for all observed land pixels.\r\n\r\nCompared with SCFG CRDP v3.0 (https://catalogue.ceda.ac.uk/uuid/80567d38de3f4b038ee6e6e53ed1af8a/) the SCFG CRDP v4.0 includes the following improvements: \r\n•\tmore permissive pre-classification allowing more pixels to enter the SCFG retrieval; \r\n•\tcorrection function applied to spectral reflectance for improved SCFG retrieval at low solar illumination conditions;\r\n•\tupdated spectral reflectance layers for snow free ground and snow free forest to improve SCFG retrieval;\r\n•\tupdated uncertainty estimation to account for the changes in the SCFG retrieval;\r\n•\timproved merging method for generating daily global SCFG products;\r\n•\tupdated salt lake mask;\r\n•\textended time series, to December 2023.\r\n\r\nThere are several days with no MODIS acquisitions in the years 2000, 2001, 2002, 2003, 2008, 2016 and 2022. In addition, on multiple days between 2000 and 2006 and in 2023, as well as on single days in 2012, 2015 and 2016, 2018, and 2020, the available MODIS data exhibit either limited spatial coverage, or corruption during data download. SCFG products are provided for all of these days, but they contain data gaps.\r\n\r\nThe SCFG product is aimed to support cryosphere and climate research applications, including variability and trend analyses, climate modelling and studies in hydrology, meteorology, and ecology.\r\nENVEO leads the SCFG product development and product generation from MODIS data, with contributions on the product development from Syke.",
    "keywords": "ESA, CCI, Snow, Snow Cover Fraction",
    "publicationState": "citable",
    "dataPublishedTime": "2025-12-03T17:20:59",
    "doiPublishedTime": "2025-12-03T17:24:16",
    "updateFrequency": "notPlanned",
    "status": "ongoing",
    "result_field": {
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        "dataPath": "/neodc/esacci/snow/data/scfg/MODIS/v4.0/",
        "oldDataPath": [],
        "storageLocation": "internal",
        "storageStatus": "online",
        "volume": 879557188025,
        "numberOfFiles": 8644,
        "fileFormat": "NetCDF"
    },
    "timePeriod": "https://api.catalogue.ceda.ac.uk/api/v2/times/12815/?format=api",
    "geographicExtent": "https://api.catalogue.ceda.ac.uk/api/v2/bboxes/2614/?format=api",
    "nonGeographicFlag": false,
    "phenomena": [
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    "dataLineage": "The snow_cci SCFG products from MODIS are based on the MODIS/Terra Calibrated Radiances 5-Min L1B Swath 1km (MOD021KM) and the MODIS/Terra Geolocation Fields 5-Min L1A Swath 1km (MOD03) Collection 6.1 data sets, provided by NASA.\r\nThe snow_cci SCF processing chain for MODIS includes the masking of clouds, the pre-classification of largely snow free areas, and the classification of snow cover fraction per pixel for all remaining observed pixels. Permanent snow and ice areas as well as water bodies are masked in the SCFG products using the corresponding classes from the Land Cover CCI map of the year 2000 as auxiliary layers. Salt lakes are masked based on a manual delineation of such areas from Terra MODIS data. \r\nSCFG products from individual tiles are merged into daily global SCFG products.\r\nAll SCFG products are prepared according to the CCI data standards.\r\nAn automated and a manual quality check was performed on the full time series.\r\nWe acknowledge Norsk Regnesentral (Norwegian Computing Center, NR) for downloading the MODIS data from NASA, and UNINETT Sigma2 AS (Sigma2, The Norwegian e-infrastructure for Research & Education) for providing the processing infrastructure for the CRDP generation from MODIS.",
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    "language": "English",
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