Data Description

This page describes the HydroLand output variables and derived indicators, their units and conventions, the spatial and temporal coverage, and the file formats and naming conventions.

Output variables

HydroLand produces two families of gridded NetCDF output files. The mesoscale Hydrologic Model (mHM) simulates land-surface hydrology, including soil water storage, evapotranspiration, and runoff generation. The multiscale Routing Model (mRM) routes the simulated runoff through the river network to produce routed river discharge.

Two settings determine how time appears in HydroLand output files. The run frequency controls how often HydroLand is executed and packaged (day or month). The output time step controls the temporal resolution written inside the files (daily or hourly), depending on the incoming OPA data and the HydroLand configuration. For example, a monthly run can write one monthly file containing daily or hourly time steps, while a daily run writes a one-day file with daily or hourly time steps.

mHM flux and state files

These files contain gridded land-surface states and fluxes produced by mHM at the configured output time step. They describe how water is stored in the soil, returned to the atmosphere, and generated as runoff before routing.

Variable	Description	Unit
SWC_L01, SWC_L02, SWC_L03	Soil water content (3 layers)	mm
aET	Actual evapotranspiration	mm day⁻¹
Q	Total runoff	mm day⁻¹

mRM routing files

These files contain gridded routed river discharge produced by mRM from the mHM runoff output. They follow the same run frequency and output time step as the corresponding HydroLand run.

Variable	Description	Unit
Qrouted	Routed river discharge	m³ s⁻¹

Indicator products

Indicator files are period-summary products derived from the mHM and mRM outputs. They are not continuous flux files; they summarise flood, drought, aridity, and soil-moisture conditions over the supplied historical or projection period.

Indicator	Description	Output unit
HydroLand aridity indicator	Ratio of mean annual actual ET to mean annual precipitation	dimensionless
Soil moisture deficit	Time-mean deficit below the fitted long-term soil moisture trend	mm
Discharge percentiles	p1, p5, p10, p90, p95, p99 threshold values from routed discharge	m³ s⁻¹
Flood/drought event count	Number of distinct events above/below the selected percentile threshold	count
Flood/drought duration	Total number of event time steps	days or hours
Flood/drought intensity	Accumulated exceedance or deficit relative to the threshold	m³ s⁻¹ × time step

The algorithms behind the indicator products are described in Technical Documentation.

Spatial coverage and resolution

• Domain: global (land surface).

• Resolutions: 0.1° (≈ 10 km) and 0.05° (≈ 5 km).

• mRM routing subdomains: 53 (0.1° setup) or 26 (0.05° setup) basin-based partitions, merged into a single global product.

Temporal coverage and resolution

• Period: historical (1990–2014) and projection (2015–2049).

• Run frequency: day or month, controlling whether HydroLand writes one-day files or files covering a full month.

• Output time step: daily or hourly, controlling the temporal resolution of the data stored inside each file.

File formats and naming conventions

All outputs are NetCDF (.nc) with CF-compliant metadata. Attributes are inherited from the driving climate forcing (activity, experiment, generation, model, realization, stream, resolution) together with the global attribute application = "HydroLand".

mHM flux files:

YYYY_MM_DD_to_YYYY_MM_DD_mHM_Fluxes_States.nc                      (daily)
YYYY_MM_DD_T00_00_to_YYYY_MM_DD_T23_00_mHM_Fluxes_States.nc        (hourly)

mRM flux files:

YYYY_MM_DD_to_YYYY_MM_DD_mRM_Fluxes_States.nc
YYYY_MM_DD_T00_00_to_YYYY_MM_DD_T23_00_mRM_Fluxes_States.nc

Indicator files:

YYYY_YYYY_aridity_index.nc
YYYY_YYYY_<Nth>_percentile_discharge_indicators.nc                 (e.g. 90th, 5th)

HydroLand output is published on the DestinE Data Lake under the collection identifier EO.UFZ.DAT.HYDROLAND. Different model experiments appear as separate items, so users can identify the experiment, period, and realization they need. Further access notes and STAC metadata conventions are described in Examples.