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Summary

The following is a description of the latest operational release of EFAS v4.8. For EFAS v5.2, which was launched on 13 August 2024. For an overview of other EFAS releases, please see: EFAS versioning system. 

Summary

EFAS v4.8 integrates changes in its meteorological forcing 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 EFAS:

• Hydrological monitoring:
  • No change in the observation-forced hydrological reanalysis simulations and the ECMWF-HRES-forced forecast initialisation (the so-called fill-up, where observations not yet available).
• Real time forecasts:
  • The spatial resolution of the forcing increases from 18 km to 9 km for the medium-range EFAS forecasts.
  • The sub-seasonal EFAS forecasts are now produced every day, instead of only twice a week for Mondays and Thursdays. The meteorological forcing comes from the new extended range forecasts in 48r1, produced every day for the 00 UTC cycle, on the same 36 km spatial resolution as before.
• Reforecasts:
  
  • EFAS v4.8 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.

Technical details

v5.2 introduces several minor changes to the system, including:

• Revised Notification criteria for Formal and Informal notifications: 
  
  • Optimised criteria for the issue of Formal and Informal notifications are based on a new methodology for the computation of the total probability of exceedance of the 5 yr RP threshold of the grand ensemble encompassing all Numerical Weather Predictions.
    
  • Improved definition of the area of validity of Formal and Informal notifications.
  • Revised layers in the EFAS Map Viewer: 
    • (a)  5-year exceedance < 48 h and 5-year exceedance > 48 h replace the layers Flood Probability < 48 h and Flood Probability > 48 h, respectively;
    • (b) Flood probability layer replaces the former Flood probability persistence layer; 
    • (c) Reporting Points pop-up window has been updated to show total probability and grand ensemble.
  • Improved EFAS notifications email to include a link to a preview feature in the Notifications Archive.

• Stations metadata have been updated to better align them with the hydrological data collected by EHDCC.
• Updated flood protection levels layer using new information in EU member states
• Updated Major Rivers layer derived from 4 different datasets: FAO AQUASTAT, EU hydro, Natural Earth, and GRDC; improved visualisation of river network and river names.
  
• Updated documentation on FTP Access

This upgrade of EFAS has no impact on the EFAS modelling results.

Technical details

EFAS v4.7 enables the visualisation of the new Global Flood Monitoring (GFM) products in the CEMS EFAS map viewer. The GFM provides continuous monitoring of floods worldwide, by automatically processing and analysing in near real-time all incoming Synthetic Aperture Radar imagery acquired by the EU’s Copernicus Sentinel-1 satellites. Here is a summary of the main changes:

The GFM product is based on 3 different flood detection algorithms running in parallel and is composed by 11 different layers, roughly grouped into 4 categories: water bodies (Observed Flood Extent, Observed Water Extent, Reference Water Mask), uncertainty-related (Exclusion mask, Uncertainty values, Advisory flags), S1 data specifics (metadata, footprint, schedule) and impacts estimate (Affected population, Affected land cover).

With a spatial resolution of 20m and a revisit time ranging from 3 to 14 days depending on S-1 overpasses, the full dataset of the product output layers is made available in raster format both separately and in bulk.

The information about the specifics of the GFM products and how to access the data are provided through the GFM Product User Manual and the Product Description Document available here

Technical details