Data Description

This page describes the HydroMet variables, units, conventions, spatial and temporal characteristics, and file formats.

Available variables

The output of HydroMet can be categorised into two groups:

The first group includes variables associated with the modelled extreme value distribution and the derived strength of extreme events. The second group includes the catalogue of all events.

Note

For additional information about the data, see the information on the Data Lake (visible only with a login) HydroMet Data Lake.

Extreme value distribution and precipitation strength

HydroMet fits an extreme value distribution to precipitation simulated by climate models. It is described by different parameters, xi, alpha, theta, eta saved in netCDF together with the intensity annual maxima Series (iams) and its balance factor beta. Since all simulation data is taken into account, there is only one file for the whole experiment in the format of YYYY_MM_DD_T00_00_to_YYYY_MM_DD_T00_00_KO_params.nc

From the GEV, Depth-Duration-Frequencies (DDF) are derived, which are provided in a file with the format YYYY_MM_DD_T00_00_to_YYYY_MM_DD_T00_00_DDF.nc. They allow for determining the expected rainfall depth for a particular duration and return period of an extreme precipitation event. The return periods are predefined (1, 2, 3, 5, 10, 20, 30, 50, 100 years).

HydroMet netCDF output

Variable

Short name

Unit

Dimensions

Description

Intensity annual maxima series

iams

mm

time, durations, lat, lon

Maximum rainfall amount in each year for a specific duration.

Depth-Duration-Frequency

DDF

mm

return_time, durations, lat, lon

Rainfall depth associated with a specific return time and event duration.

Location parameter xi

xi

dimensionless

lat, lon

Location parameter of the Generalized Extreme Value (GEV) distribution.

Scale parameter alpha

alpha

dimensionless

lat, lon

Scale parameter of the Generalized Extreme Value (GEV) distribution.

First Koutsoyiannis parameter theta

theta

dimensionless

lat, lon

Additional parameter of the Generalized Extreme Value (GEV) distribution.

Second Koutsoyiannis parameter eta

eta

dimensionless

lat, lon

Additional parameter of the Generalized Extreme Value (GEV) distribution.

Balancing parameter beta

beta

dimensionless

time, durations, lat, lon

Balancing parameter for the Intensity Annual Maxima Series.

Extreme event catalogue

Building on the parameters and the DDF, HydroMet’s main output is an event catalogue that tracks all extreme precipitation events in the observed region. Only events that pass the threshold of a 5-year return period are considered. The process also includes a filtering of overlapping objects, which selects the object with the highest extreme value. The data is presented in CSV format, listing the events with their characteristics:

  • Object_ID: Code for the object the event was selected from, comprised of end date in numerical form, duration window in hours, and a running number.

  • Event_ID: Code for the event, comprised of return period, selection parameter and running number.

  • Start_Time: Start date of event.

  • End_Time: End date of event.

  • Duration: Duration of event [hours].

  • Area: Number of pixels included within event [in 25 km²].

  • RRmean: Mean precipitation amount within event [mm].

  • Tmean_KOSTRA: Mean return period of the event [years].

  • Eta_KOSTRA: Extremity of event [dimensionless].

  • RRmax: Maximum precipitation within the event [mm].

  • RR_Tmax: Precipitation amount with the maximum return period [mm].

  • Tmax_KOSTRA: Maximum return period within the event [years].

  • x_center: Pixel number on x-axis of the event centre.

  • y_center: Pixel number on y-axis of the event centre.

  • lon_center: Longitude of the event centre.

  • lat_center: Latitude of the event centre.

  • x_RRmax: Pixel number on the x-axis of the maximum precipitation within the event.

  • y_RRmax: Pixel number on the y-axis of the maximum precipitation within the event.

  • lon_RRmax: Longitude of the maximum precipitation within the event.

  • lat_RRmax: Latitude of the maximum precipitation within the event.

  • MPP_flag: Flag indicating a data anomaly. Set to 1 when the Maximum Pixel Precipitation (MPP) threshold is exceeded.

Spatial and temporal coverage

HydroMet output is currently provided over Europe on a regular latitude/longitude grid at the native resolution of the climate model (~5km). The temporal extent of the data is the same as the temporal extent of the climate simulations simulations . The files are not split; therefore, each file covers the entire simulation period.

File formats

The output describing the Extreme value distribution is provided as netCDF while the catalogue is a CSV.