ERA5_sl

{
  "kind": "grid",
  "source": {
    "url_template": "https://data.earthsci.dev/era5/era5_sl_{date:%Y}_{date:%m}.nc"
  },
  "temporal": {
    "start": "1940-01-01T00:00:00Z",
    "end": "2025-12-31T23:59:59Z",
    "file_period": "P1M",
    "frequency": "PT1H",
    "records_per_file": 744,
    "time_variable": "valid_time",
    "records_per_sample": 2
  },
  "reference": {
    "citation": "Hersbach, H. et al. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049.",
    "url": "https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-v5",
    "doi": "10.1002/qj.3803"
  },
  "metadata": {
    "tags": [
      "era5",
      "ecmwf",
      "meteorology",
      "reanalysis",
      "global",
      "single-level",
      "surface",
      "hourly",
      "0.25deg"
    ],
    "native_resolution_deg": {
      "longitude": 0.25,
      "latitude": 0.25
    },
    "native_extent": {
      "longitude": [
        -180.0,
        180.0
      ],
      "latitude": [
        -90.0,
        90.0
      ]
    },
    "native_staggering": "All variables are cell-centered (longitude/latitude 'center') — ERA5 is stored on a regular non-staggered grid. Single-level surface fields (2 m T/Td, 10 m u/v) have no vertical dimension.",
    "netcdf_dimensions": [
      "longitude",
      "latitude",
      "valid_time"
    ],
    "file_naming": "era5_sl_{YYYY}_{MM:02d}.nc (monthly, one file per calendar month, the four single-level variables; NO pressure_level dimension)",
    "access_note": "ERA5 data is available from the Copernicus Climate Data Store (CDS) at https://cds.climate.copernicus.eu/. The url_template above uses a placeholder earthsci.dev mirror; in production, set EARTHSCIDATADIR to a local cache directory populated via the CDS API.",
    "cds": {
      "dataset": "reanalysis-era5-single-levels",
      "format": "netcdf",
      "description": "Opt-in CDS request descriptor. When the loader seam is routed through the EarthSciIO provider adapter, this block makes the loader resolve to the real Copernicus CDS API: the adapter builds a per-month `cds://reanalysis-era5-single-levels?<request>` URL whose `area` is the simulation domain's WGS84 bounding box and whose `variable` list maps this loader's short names (t2m, u10, v10, d2m) to the CDS single-level long names (2m_temperature, 10m_u_component_of_wind, 10m_v_component_of_wind, 2m_dewpoint_temperature). There is NO `pressure_level` key — the single-levels dataset rejects it. EarthSciIO's registered `cds` transport submits/polls/downloads the NetCDF asset, authenticating with the PRIVATE-TOKEN from ~/.cdsapirc or $CDSAPI_KEY."
    },
    "temporal_note": "ERA5 monthly files are released with a ~2-month lag. The temporal.end above is approximate; update as new months are released. ERA5 Back Extension covers 1940–1978; the main ERA5 record begins January 1979.",
    "merged_from": "components/earthsci_data/era5_single_loader.esm",
    "merge_note": "Merged from the standalone pure-I/O file components/earthsci_data/era5_single_loader.esm, which is deleted by the same commit. The 0.x `X.esm` + `X_loader.esm` split existed only because a loader was a COMPONENT and a {\"ref\"} target had to contain exactly one component. At esm 1.0.0 a data source is NOT a component, not a coupling endpoint and not a scoped-name path root, and `data_sources` no longer counts toward a file's top-level system count — so one file may hold a model AND the data_sources that model consumes and still be mountable by {\"ref\"}. This registry entry is byte-identical to the one the deleted file declared (it was already mirrored here so this document would validate), and the deleted file's own top-level metadata — name, description, tags, created, authors, references — is preserved verbatim in `merged_file_metadata` so no provenance, citation or migration note is lost.",
    "merged_file_metadata": {
      "name": "ERA5_sl_loader",
      "description": "Pure-I/O data loader for ERA5 ECMWF Reanalysis 5th Generation SINGLE-LEVEL (surface) fields. Provides hourly near-surface atmospheric variables — 10 m wind (u10, v10), 2 m temperature (t2m) and 2 m dewpoint temperature (d2m) — on the native 0.25°×0.25° global longitude/latitude grid, 1940–present, sourced from monthly NetCDF files. This is the single-level counterpart of era5_loader.esm (which reads pressure-level fields); it is used where genuine near-surface met is needed over terrain, because a 1000 hPa pressure level is at or below ground over elevated terrain and its fields are extrapolated there.\n\nThis is the loader half of the era5 loader+regridding-model split (RFC pure-io-data-loaders §4.1/§7). It is PURE I/O: it declares its source (url_template), the file variables it reads (with units), and its temporal cadence. It performs NO reprojection and NO regridding — those are per-variable concerns of the regridding model (components/earthsci_data/era5_single.esm), which references this file as a subsystem via {\"ref\": \"./era5_single_loader.esm\"}.\n\nBecause a `temporal` block is present, this loader seeds DISCRETE cadence for its variables: the runtime refreshes the file buffers hourly. (A consumer that needs a single time slice as a static field — e.g. the wildlandfire.esm surface-met coupling — binds one resolved hour as a CONST provider.)\n\nRelative humidity is NOT a single-level ERA5 variable; downstream consumers DERIVE RH from t2m + d2m via the Magnus/Tetens formula (see era5_single.esm / the wildlandfire Era5Regrid model).\n\nCDS dataset: reanalysis-era5-single-levels (no pressure_level key). Migrated from EarthSciData.jl ERA5FileSet conventions; the single-level variable set follows the CDS single-level short names t2m/u10/v10/d2m.",
      "tags": [
        "earthsci_data",
        "meteorology",
        "reanalysis",
        "era5",
        "ecmwf",
        "single_levels",
        "surface",
        "global",
        "data_loader",
        "pure-io",
        "longlat"
      ],
      "created": "2026-07-12T00:00:00Z",
      "authors": [
        "ECMWF",
        "EarthSciModels"
      ],
      "references": [
        {
          "citation": "Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horanyi, A., Munoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., et al. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049.",
          "url": "https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-v5",
          "doi": "10.1002/qj.3803"
        }
      ]
    }
  }
}