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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 7 | Copyright

Special issue: 11th Plinius Conference on Mediterranean Storms

Nat. Hazards Earth Syst. Sci., 10, 1443-1455, 2010
https://doi.org/10.5194/nhess-10-1443-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  07 Jul 2010

07 Jul 2010

Improving QPF by blending techniques at the Meteorological Service of Catalonia

A. Atencia1,2, T. Rigo1, A. Sairouni1, J. Moré1, J. Bech1, E. Vilaclara1, J. Cunillera1, M. C. Llasat2, and L. Garrote3 A. Atencia et al.
  • 1Meteorological Service of Catalonia, Spain
  • 2Department of Astronomy and Meteorology, Faculty of Physics, University of Barcelona, Spain
  • 3Department of Hydraulic and Energy Engineering, Technical University of Madrid, Spain

Abstract. The current operational very short-term and short-term quantitative precipitation forecast (QPF) at the Meteorological Service of Catalonia (SMC) is made by three different methodologies: Advection of the radar reflectivity field (ADV), Identification, tracking and forecasting of convective structures (CST) and numerical weather prediction (NWP) models using observational data assimilation (radar, satellite, etc.). These precipitation forecasts have different characteristics, lead time and spatial resolutions. The objective of this study is to combine these methods in order to obtain a single and optimized QPF at each lead time. This combination (blending) of the radar forecast (ADV and CST) and precipitation forecast from NWP model is carried out by means of different methodologies according to the prediction horizon. Firstly, in order to take advantage of the rainfall location and intensity from radar observations, a phase correction technique is applied to the NWP output to derive an additional corrected forecast (MCO). To select the best precipitation estimation in the first and second hour (t+1 h and t+2 h), the information from radar advection (ADV) and the corrected outputs from the model (MCO) are mixed by using different weights, which vary dynamically, according to indexes that quantify the quality of these predictions. This procedure has the ability to integrate the skill of rainfall location and patterns that are given by the advection of radar reflectivity field with the capacity of generating new precipitation areas from the NWP models. From the third hour (t+3 h), as radar-based forecasting has generally low skills, only the quantitative precipitation forecast from model is used. This blending of different sources of prediction is verified for different types of episodes (convective, moderately convective and stratiform) to obtain a robust methodology for implementing it in an operational and dynamic way.

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