Abstract
The incorporation of numerical weather predictions (NWP) into a flood forecasting system can increase forecast lead times from a few hours to a few days. A single NWP forecast from a single forecast centre, however, is insufficient as it involves considerable non-predictable uncertainties and lead to a high number of false alarms. The availability of global ensemble numerical weather prediction systems through the THORPEX Interactive Grand Global Ensemble’ (TIGGE) offers a new opportunity for flood forecast. The GMKHM distributed hydrological model, which is based on a mixed runoff generation model and overland flow routing model based on kinematic wave theory, and the topographical information of each grid cell extracted from the Digital Elevation Model (DEM), is coupled with ensemble weather predictions based on the TIGGE database (CMC, CMA, ECWMF, UKMO, NCEP) for flood forecast. This paper presents a case study using the coupled flood forecasting model on the Xixian catchment (a drainage area of 8826 km2) located in Henan province, China. A probabilistic discharge is provided as the end product of flood forecast. Results show that the association of the GMKHM model and the TIGGE database gives a promising tool for the anticipation of flood events several days ahead,, comparable with that driven by raingauge observation.
Highlights
Flood protection and awareness have continued to rise on the political agenda accompanied by a drive to “improve” flood forecasts (Demeritt et al, 2007; DKKV, 2004; Parker and Fordham, 1996; Pitt, 2007; van Berkom et al, 2007; Cloke and Pappenberger, 2009)
The precipitation forecasts Pf were retrieved from five weather centres in the THORPEX Interactive Grand Global Ensemble’ (TIGGE) archive, namely Canadian Meteorological Centre (CMC), China Meteorological Administration (CMA), European Centre for MediumRange Weather Forecasts (ECMWF), UK Met Office (UKMO), and National Centres of Environmental Prediction (NCEP)
A coupled atmospheric-hydrologic flood forecast model driven by the TIGGE ensemble forecasts is set up to study the potential benefits of using the TIGGE database in flood forecasting in the upper reaches of Xixian catchment during the 2007 flood seasons
Summary
Flood protection and awareness have continued to rise on the political agenda accompanied by a drive to “improve” flood forecasts (Demeritt et al, 2007; DKKV, 2004; Parker and Fordham, 1996; Pitt, 2007; van Berkom et al, 2007; Cloke and Pappenberger, 2009). Ensemble Prediction Systems (EPS) have evolved over the last decade to simulate the effect on weather forecasts of observation uncertainties, model uncertainties (e.g. due to a lack of resolution, simplified parameterization of physical processes and effect of unresolved processes), imperfect boundary conditions and data assimilation assumptions (Park et al, 2007). An ensemble of weather forecasts can be used on catchment hydrology and provide improved early flood forecasting as some of the uncertainties can be quantified (Cloke and Pappenberger, 2008). To this end, a case study was carried out using five TIGGE forecast centres. The aims of this paper are to (1) develop atmospheric-hydrologic flood forecasting model cascade driven by TIGGE ensemble forecasts, and (2) apply the model cascade to the Xixian catchment and compare the simulation results driven by TIGGE forecasts and raingauge observation
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