GloFAS Seasonal v2.0

GloFAS Seasonal v2.0 was launched on 14 November 2018, with the first GloFAS Seasonal v2.0 forecasts available for Dec 2018.

GloFAS Seasonal v2.0 technical settings

GloFAS Seasonal 2.0 uses the Lisflood river routing model (van der Knijff et al., 2010) to propagate along the river channel the surface and sub-surface runoff forecasts of the HTESSEL land surface model (Balsamo et al., 2009) of the ECMWF SEAS5 seasonal forecasting system and to produce daily discharge forecasts. In GloFAS Seasonal v2.0, Lisflood is calibrated for better accounting of the variability in the hydrological processes (Hirpa et. al., 2018). More details can be found in the Lisflood calibration page. Results are presented as weekly averages, starting every Monday.

SEAS5 runoff ensemble has 51 members at ~36 km horizontal resolution, which are resampled to 0.1 spatial resolution (~10 km) before being used as daily input to Lisflood. In GloFAS Seasonal v2.0, only the first 16 weeks (out of the available 7 months) of SEAS5 are used.

GloFAS Seasonal v2.0 initial conditions (atmosphere and land surface states from which to start the ensemble discharge forecast) are based on a monitoring analysis of the latest observations, the ERA5 ECMWF reanalysis. In practice, GloFAS Seasonal v2.0 initial conditions are taken as GloFAS 30-day v2.0 hydrological reanalysis generated in near-real time.

The GloFAS system
Schematic of GloFAS Seasonal v2.0 operational.

GloFAS Seasonal v2.0 reference discharge runs

GloFAS Seasonal v2.0 reference discharge runs are a collection of discharge simulations as close as possible to GloFAS Seasonal v2.0 operational system.

GloFAS Seasonal v2.0 hydrological reanalysis is based on ERA5, the latest atmospheric reanalysis product of ECMWF available in 2018. ERA5 has a horizontal resolution of ~32 km (see Hersbach and Dee 2016 for further reading). GloFAS Seasonal v2.0 hydrological reanalysis covers 1981-2017. GloFAS Seasonal v2.0 hydrological reanalysis is identical to GloFAS 30-day v2.0 hydrological reanalysis.

GloFAS Seasonal v2.0 forecast reruns are forecast simulations performed for a set of past dates (1981-2017) using ECMWF Seasonal forecasting system SEA5, based on a configuration as close as possible to GloFAS Seasonal operational setting. They are initialised using GloFAS Seasonal v2.0 hydrological reanalysis. They are used for the GloFAS Seasonal v2.0 discharge thresholds and to analyse GloFAS Seasonal v2.0 forecast skill systematically over a long period.

GloFAS Seasonal v2.0 discharge thresholds are discharge magnitude corresponding to fixed percentile values, derived from the 37-year GloFAS Seasonal v2.0 forecasts reruns separately for each week of the year and lead-time. GloFAS Seasonal v2.0 discharge thresholds are used to generate river flow anomaly forecast maps.

GloFAS Seasonal v2.0 products

GloFAS Seasonal v2.0 products are generated by comparing, for each lead-time to 16 weeks, the 51 scenarios of GloFAS Seasonal v2.0 weekly-averaged river discharge forecasts to the corresponding GloFAS Seasonal v2.0 discharge thresholds. They include exceedance probability maps and weekly forecast hydrographs, and are available on the 10th of each month through the GloFAS map viewer.

GloFAS Seasonal v2.0 available data

GloFAS Seasonal v2.0 available data is summarised in the table below. It contains the period covered, the production frequency, the number of ensemble members and the ECMWF IFS versions used for each dataset. Note that GloFAS Seasonal v2.0 datasets only include weekly-averaged discharge time series.

GloFAS Seasonal v2.0 Period Frequency Ensemble members ECMWF IFS version
Reanalysis See GloFAS 30-day v2.0 hydrological reanalysis
Forecasts reruns Jan 1981 - Oct 2017 Monthly 25 SEAS5
Real-time forecasts Nov 2018 - real-time Monthly 51 43r1

GloFAS Seasonal v2.0 skill

GloFAS Seasonal v2.0 evaluation is currently underway. Results will be published as soon as available.