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History of modifications
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List of datasets covered by this document
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Related documents
| Reference ID | Document | ||||||
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D1
| NGCD Algorithm Theoretical Basis Document | ||||||
D2
| Climate and Forecast (CF) Conventions and Metadata; http://cfconventions.org | ||||||
D3
| R Core Team (2017). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/ |
Acronyms
Acronym | Definition |
CDS | |
MET Norway | |
FMI | |
KNMI | |
SMHI | |
NGCD | Nordic Gridded Climate Dataset (DOI:https://doi.org/10.24381/cds.e8f4a10c |
NGCD-1 | NGCD type 1 datasets |
NGCD-2 | NGCD type 2 datasets |
seNorge | Observational gridded dataset over Norway (senorge.no) |
ECA&D | |
TITAN | |
OI | Optimal Interpolation |
| RMSE | Root Mean Squared Error |
General definitions
Symbol | Definition |
TG | Daily mean temperature (from day before the date in the timestamp at 06 UTC, to date in the timestamp at 06 UTC) |
TX | Daily maximum temperature (from day before the date in the timestamp at 18 UTC, to date in the timestamp at 18 UTC) |
TN | Daily minimum temperature (from day before the date in the timestamp at 18 UTC, to date in the timestamp at 18 UTC) |
RR | Daily precipitation total (from day before the date in the timestamp at 06 UTC, to date in the timestamp at 06 UTC) |
Data access information
Anchor table_data_access table_data_access
| Description | Link |
|---|---|
The historical archive for different versions is made available to users via the CDS | https://cds.climate.copernicus.eu/cdsapp#!/dataset/insitu-gridded-observations-nordic |
| The data are also available to users via MET Norway OPeNDAP access | https://thredds.met.no/thredds/catalog/ngcd/catalog.html |
| MET Norway. Historical archive ver. 22.03 (for different versions, replace 22.03 with the correct label) | https://thredds.met.no/thredds/catalog/ngcd/version_22.03/catalog.html |
| MET Norway. Provisional archive | https://thredds.met.no/thredds/catalog/ngcd/provisional/catalog.html |
The list of Known issues is available at the following link.
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NGCD is fully updated twice a year, in March and September. Each update yields a new version, which is labelled as Year.Month (e.g. the update in March September 2022 yields ver. 22.0309). This document has been updated to NGCD ver. 22.0309.
Each version is made up of two archives: i) the historical archive and ii) the provisional archive.
In the case of ver. 22.0309:
- The historical archive covers the 51-year time period that ranges from January 1971 to 2021June 2022. Any changes made in post-production on the historical archive are reported on the List of Known issues and/or in the "Known issues" section on the NGCD page on the MET Norway thredds server.
- The provisional archive includes NGCD-2 files only. It begins with files of the 1st of January July 2022 and is regularly updated every day, such that some of the files (i.e. usually the most recent ones) may change from day to day, without any particular warnings. The products are obtained using the same methods as for the historical archive of NGCD-2. However, the observations used as input data are retrieved from the open data application programming interfaces of: FMI, MET Norway and SMHI. The provisional archive for the period from January July to June December 2022 will be replaced by the historical archive of the next NGCD version.
The data can be found at the links specified in the Data access information. The main description of NGCD is in the Product information section. Then, Appendix A reports the evaluation made for ver. 18.03, which shares the same methods used for all versions up to ver. 22.0309. Appendix B contains examples of the file structures.
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The time series of the number of stations used for the production of NGCD ver 22.03 09 are shown in Figures 1-4 for RR, TG, TN and TX, respectively. The number of RR stations in the region decreases, from 2400 2600 stations-per-day in 1971 to 1500 stations-per-day in 2020 (≅ -60%42%). For TG, the situation is the opposite and the number of stations grows after 2010, from 800 stations-per-day in 2000 to 1300 1400 stations-per-day in 2020 (≅ +60%75%). The main reason for the increase is the inclusion of sub-regional networks over Norway, managed by Norwegian public institutions. Note that the number of stations used in the production of TG after 2010 has a larger day-to-day variability than before. TX and TN undergo a gradual decrease in the number of stations from 1971 to 1994, which is followed by a turnaround with gradual growth from 1995 onwards. Then, for 2021 and 2022 the input datasets align -rather abruptly- with that used for TG. Between 1971 and 2020, the relative variations for TX and TN are more limited than for TG, with the minimum number around 700 stations-per-day and the maximum 950 1000 stations-per-day (≅ +35%43%). In 2021 and 2022, there are more stations available than in 2020, for all variables.
Anchor figure1 figure1
Figure 1: Daily precipitation total (RR): monthly time series of the number of stations used in the production of NGCD ver 22.03 09 from January 1971 to December 2021June 2022. For each month, the number of stations shown is the median of the stations available daily.
Anchor figure2 figure2
Figure 2: Daily mean temperature (TG): monthly time series of the number of stations used in the production of NGCD ver 22.03 09 from January 1971 to December 2021June 2022. For each month, the number of stations shown is the median of the stations available daily.
Anchor figure3 figure3
Figure 3: Daily minimum temperature (TN): monthly time series of the number of stations used in the production of NGCD ver 22.03 09 from January 1971 to December 2021June 2022. For each month, the number of stations shown is the median of the stations available daily.
Anchor figure4 figure4
Figure 4: Daily maximum temperature (TX): monthly time series of the number of stations used in the production of NGCD ver 22.03 09 from January 1971 to December 2021June 2022. For each month, the number of stations shown is the median of the stations available daily.
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For RR, the number of stations decreases over the years and the impact is clearly visible both in the map and, especially, over the range of elevations not covered properly by the observational network. In the north, more than half of the elevation range (i.e. the higher elevations) is not covered by the network. In the case of TG, the increase in the number of stations is concentrated over Norway and the range of elevations is more uniformly sampled than for RR. For TN (and TX), the situation is similar to TG, except that until 2021 the observational network over Norway is less dense. In From 2021, the observational network is similar for all temperature variables.
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- <Var> is one of: RR, TG, TX and TN
- <Id_type> is either 1 or 2
- <ver> is the version label in the format Year.Month (e.g. 22.0309)
- <Date> is in the form YYYYMMDD
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The key fields provided in this product are as given in Table 1.
Table 1: Key data fields in the output files.Anchor table1 table1
Variable Name | Description |
lon | longitudes of the grid points |
lat | latitudes of the grid points |
projection_laea | specification of the coordinate reference system |
time_bounds | time bounds of the aggregated variable |
daily variable in the file |
The data are provided on a single layer, near the surface, and on a regular grid covering Finland, Norway and Sweden. The grid is masked outside the domain and over the sea, where no in-situ observations are available, apart from a buffer extending over the sea for a few kilometers. The coordinate reference system is the Lambert Azimuthal Equal Area projection and the grid has a resolution of 1 km in both the Easting and Northing directions. The dimension of the data field is 1550 in the Easting and 2020 in the Northing. The spatial domain is shown in Figures 5-7.
When downloading files from the CDS, users obtain one file for each: day, variable and NGCD-type requested. The fields also have a time dimension, which always has a length of one.
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Appendix B - Example file structure
Example file structure can be seen directly from the web-browser at the following URLs.
Var | URL with example of file structure |
RR |
TG |
TX |
TN |
References
Klein Tank, A. M., Wijngaard, J. B., Können, G. P., Böhm, R. , Demarée, G. , Gocheva, A. , Mileta, M., Pashiardis, S. , Hejkrlik, L. , Kern‐Hansen, C. , Heino, R. , Bessemoulin, P. , Müller‐Westermeier, G. , Tzanakou, M. , Szalai, S. , Pálsdóttir, T. , Fitzgerald, D. , Rubin, S. , Capaldo, M. , Maugeri, M. , Leitass, A. , Bukantis, A. , Aberfeld, R. , van Engelen, A. F., Forland, E. , Mietus, M. , Coelho, F. , Mares, C. , Razuvaev, V. , Nieplova, E. , Cegnar, T. , Antonio López, J. , Dahlström, B. , Moberg, A. , Kirchhofer, W. , Ceylan, A. , Pachaliuk, O. , Alexander, L. V. and Petrovic, P. (2002), Daily dataset of 20th‐century surface air temperature and precipitation series for the European Climate Assessment. Int. J. Climatol., 22: 1441-1453. doi:10.1002/joc.773
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This document has been produced in the context of the Copernicus Climate Change Service (C3S). The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation agreement signed on 11/11/2014). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view. |
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