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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-572
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
26 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Seasonal Drought Prediction for Semiarid Northeast Brazil: Verification of Six Hydro-Meteorological Forecast Products
José Miguel Delgado1, Sebastian Voss1, Gerd Bürger1, Klaus Vormoor1, Aline Murawski2, Marcelo Rodrigues3, Eduardo Martins3, Francisco Vasconcelos Júnior3, and Till Francke1 1Institute of Earth and Environmental Sciences, University of Potsdam, Germany
2German Research Centre of Geosciences GFZ Potsdam, Germany
3Research Institute for Meteorology and Water Resources – FUNCEME, Fortaleza, Brazil
Abstract. A set of seasonal drought forecast models was assessed and verified for the Jaguaribe River in semiarid northeast Brazil. Meteorological seasonal forecasts were provided by the operational forecasting system used at FUNCEME (Ceará's research foundation for meteorology) and by the European Centre for Medium-Range Weather Forecasts (ECMWF). Three downscaling approaches were tested and combined with the models in hindcast mode for the period 1981 to 2014. The forecast issue time was January and the forecast period was January to June. Hydrological drought indices were obtained by fitting a generalized linear model to observations. In short, it was possible to obtain forecasts for (a) monthly precipitation, (b) meteorological drought indices, and (c) hydrological drought indices.

The skill of the forecasting systems was evaluated with regard to root mean square error (RMSE) and the relative operating characteristic (ROC) skill score. Forecasts of monthly precipitation had little or no skill considering RMSE. Still, the forecast of extreme events of low monthly precipitation showed skill for the rainy season (ROC skill score of 0.24 to 0.33). A similar picture was seen when forecasting meteorological drought indices: low skill regarding RMSE and significant skill when forecasting drought events of e.g. SPEI01 (ROC skill score of 0.53 to 0.61). Similar results were obtained for low regional reservoir storage forecasts. Regarding the skill in the forecasted months, it was greater for April, when compared to February and March (the remaining months of the rainy season). This work showed that a multimodel ensemble can forecast drought events of time scales relevant to water managers in northeast Brazil with skill. But no or little skill could be found in the forecasts of the whole range of monthly precipitation or drought indices (e.g. forecasting average years). Both this work and those here revisited showed that major steps forward are needed in forecasting the rainy season in northeast Brazil.


Citation: Delgado, J. M., Voss, S., Bürger, G., Vormoor, K., Murawski, A., Rodrigues, M., Martins, E., Vasconcelos Júnior, F., and Francke, T.: Seasonal Drought Prediction for Semiarid Northeast Brazil: Verification of Six Hydro-Meteorological Forecast Products, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-572, in review, 2017.
José Miguel Delgado et al.
José Miguel Delgado et al.
José Miguel Delgado et al.

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Short summary
The feasibility of drought prediction is assessed in the Brazilian Northeast. The models were provided by a regional and a European meteorological agency and downscaling was done using 3 empirical models. This work showed that the combination of different forecast and downscaling models can provide skillful predictions of drought events of time scales relevant to water managers. But the models also showed little to no skill for quantitative predictions of monthly precipitation.
The feasibility of drought prediction is assessed in the Brazilian Northeast. The models were...
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