D-MSSM

Product overview¶

D-MSSM is the Daily Medium-resolution Gap-filled Surface Soil Moisture product. It fuses data from SMAP, CYGNSS, Spire GNSS-R, and SMOS, then applies a machine-learning gap-filling algorithm to produce seamless daily global coverage.

Variants:

• d-mssm — Standard product with ~4-day latency

• d-mssm-nrt — Near-real-time product with ~1-day latency

Both variants share the same file structure and variable definitions. The feed field in API responses indicates the source tier ("standard" or "nrt").

NetCDF4 format¶

Global attributes¶

Variables¶

Processing flag (pflag)¶

The pflag is stored as a uint8 with a fill value of 255. It encodes quality and retrieval status per grid point.

Recommended quality is determined from the qflag. If static and/or dynamic conditions are present, the retrieval is flagged as not recommended. The retrieval-successful state is determined from the dai; when dai = 0 (no input data available), no soil moisture is retrieved and pflag is set to 3 (not recommended + not successful).

Quality flag (qflag)¶

The qflag is stored as a uint8 with a fill value of 255. It encodes static and dynamic surface conditions that may affect data quality.

Static conditions (complex topography, urban area, water bodies) do not change over time. Dynamic conditions (precipitation, snow/ice, freeze/thaw, dense vegetation) vary with each observation.

Sources of the static/dynamic conditions:

• Complex topography: Derived from the SMAP ancillary surface flag, based on slope variability from a DEM within each 36 km grid cell. Slope standard deviation > 6.0° is flagged.

• Urban areas: Derived from ESA CCI Land Cover data (300 m), downsampled to 6 km.

• Water bodies: Derived from ESA CCI WaterBodies data (300 m), downsampled to 6 km.

• Precipitation / Snow and ice: Propagated from the SMAP surface flag.

• Freeze/thaw: Transmitted from the SMAP surface flag when SMAP data is available. When SMAP data is absent, a periodic climatological layer (one value per day of year per pixel) derived from the complete SMAP historical record (2015–2022) is used.

• Dense vegetation: Derived as a periodic layer from the SMAP vegetation water content layer. Pixels are flagged when the average value exceeds 5 kg/m².

Aggregation rule: pflag for D-MSSM is the bitwise AND of the twice-daily pflag values; qflag is the bitwise OR.

Data source values¶

The data_source_am and data_source_pm variables identify the input data source for each pixel:

Data Availability Index (dai)¶

The dai indicates how recently observed input data contributed to the gap-filled product. It is the daily average of twice-daily dai values. Higher values indicate more recent observations; dai = 0 means no input data was available, resulting in no retrieval (pflag = 3).

To convert: dai_physical = raw_value × 0.01.

Advisory flag (aflag)¶

The aflag simplifies masking:

• 0 — recommended quality (use the data)

• 1 — quality not recommended (mask this pixel)

GeoTIFF format¶

D-MSSM GeoTIFF files contain color-coded soil moisture values with no-data set to 255. Conditions that prevent soil moisture retrieval (urban areas, water bodies, freeze/thaw, snow/ice) are pre-masked. Each delivery includes a corresponding advisory flag GeoTIFF layer.

CSV and GeoJSON format¶

CSV and GeoJSON files contain point time series at specific locations. The following variables are included:

JSON (point API) response¶

When queried via the /soil-moisture/point endpoint with format=JSON, the response has this structure. Note that the time field is returned as valid_time (not local_time as some older documentation may indicate):

{
  "data": [
    {
      "location": {
        "coordinates": {
          "lat": 14.0,
          "lon": 100.5
        }
      },
      "times": {
        "valid_time": "2026-02-10 12:00:00"
      },
      "values": {
        "d_mssm": 0.325,
        "pflag": 0.0,
        "qflag": 0.0,
        "data_source_am": 5.0,
        "data_source_pm": 5.0,
        "dai": 0.17,
        "lat": 14.0,
        "lon": 100.5,
        "aflag": 0,
        "feed": "standard"
      }
    }
  ],
  "meta": {
    "message": null
  }
}