The effect of reference climatology on global flood forecasting

The Global Flood Awareness System (GloFAS) is a pre-operational suite performing daily streamflow simulations to detect severe floods in large river basins. GloFAS defines the severity of a flood event with respect to thresholds estimated based on model simulated streamflow climatology. Hence, determining accurate and consistent critical thresholds is important for its skillful flood forecasting. In this work, streamflow climatology derived from two global meteorological inputs were compared, and their impacts on global flood forecasting were assessed. The first climatology is based on precipitation-corrected reanalysis data (ERA-Interim) which is currently used in the operational GloFAS forecast, while the second is derived from reforecasts which are routinely produced using the latest weather model. The results of the comparison indicate that: 1) flood thresholds derived from the two datasets have substantial dissimilarities with varying characteristics across different regions of the globe; 2) the differences in the thresholds have a spatially variable impact on the severity classification of a flood; and 3) ERA-Interim produced lower flood threshold exceedance probabilities (and flood detection rates) than the reforecast for several large rivers at short forecast lead-times, where the uncertainty in the meteorological forecast is smaller. Overall, we found that the use of reforecasts, instead of ERA-Interim, marginally improved the flood detection skill of GloFAS flood forecasts.

HIRPA Feyera Aga;  SALAMON Peter;  ALFIERI Lorenzo;  THIELEN DEL POZO Jutta;  ZSOTER Ervin;  PAPPENBERGER Florian; 

2016-04-08

AMER METEOROLOGICAL SOC

JRC94007

1525-755X,   

http://journals.ametsoc.org/doi/10.1175/JHM-D-15-0044.1,    https://publications.jrc.ec.europa.eu/repository/handle/JRC94007,   

10.1175/JHM-D-15-0044.1,