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The following is a description of the latest operational release of GloFASGloFAS v4.0, which is available as pre-release on the GloFAS Stage Platform from 05 July 2023. The full operational GloFAS v4.0 will be released soon.

For  v3.5. For an overview of other GloFAS releases, please see : GloFAS versioning system.

Summary

GloFAS v3.5 integrates changes in its meteorological forcing used for the forecasts, with the use of the new version of the ECMWF-ENS ensemble forecasting system, introduced by IFS cycle 48r1. This change in the forcing data has the following impacts on GloFAS:

• Hydrological monitoring:
  • No change in the ECMWF-C3S ERA5- and ERA5-T-forced hydrological reanalysis simulations.
  • In the forecast initialisation (in the so-called fill-up, where ERA5-T is not yet available), the meteorological forcing resolution of ECMWF-ENS-CNTL has increased from 18 km to 9 km (similarly to the real time forecasts for days 1-15).
• Real time forecasts:
  • The spatial resolution of the forcing increases from 18 km to 9 km in the first 15 days of the 30-day forecast horizon, while the resolution of the extended-range forcing (days 16 to 30) remain unchanged at 36 km.
  • The extended-range ECMWF-ENS is produced every day in 48r1. Thus, the meteorological forcing for days 16-30 in GloFAS (which is blended after the first 15 days of higher resolution ENS) will always come from 1-day old forecast runs. Previously, it was coming from 1-4-day old forecast runs, depending on the day of the week, as the extended-range ENS was produced only on Mondays and Thursdays before 48r1.
• Reforecasts:
  • GloFAS v3.5 will not have a new 48r1-specific hydrological reforecast data set.
• Seasonal forecasts and seasonal reforecasts:
  • There is no impact on the seasonal hydrological modelling system.

More details on the 48r1 meteorological modelling changes can be found on the Implementation of IFS Cycle 48r1 page.

v4.0 introduces a number of major changes to the system, including:

• higher spatial resolution. GloFAS v4.0 has 0.05 degrees resolution (~5km), as opposed to all the previous GloFAS versions having 0.1 degrees resolution (~10km).
• an entirely new set of 0.05 degrees resolution input maps produced using the most recent research findings, remote sensing, and in-situ datasets.
• major improvements to the open-source hydrological model LISFLOOD.
• a new hydrological model calibration at 1996 in-situ gauging stations. Furthermore, a parameter regionalisation was performed to estimate the parameters of catchments for which in situ discharge observations were not available.
• new return period thresholds and snow water/soil moisture anomaly maps based on a climatology from 1980 – 2022. The GloFAS v4.0 river discharge climatology is available at the C3S Climate Data Store.
• updated GloFAS Seasonal forecasts using the newly calibrated, higher resolution hydrological model.

This major version change is associated with an update of the historical hydrological reanalysis. 

This upgrade of GloFAS has large impacts on the GloFAS modelling results.

31 stations were also added to the reporting point: 9 stations in Canada, 7 stations in Russia, 4 stations in Finland, 3 stations in Argentina and 1 station in each of Brazil, United States, Morocco, Benin, Uganda, Thailand, Columbia and South AfricaIn addition, the v3.5 update also includes two additional reporting points in Bangladesh and Nigeria.

Technical details