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A new region-aware bias-correction method for simulated precipitation in areas of complex orography

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Gómez-Navarro Juan José, Raible Christoph C., Bozhinova Denica, Martius Olivia, García Valero Juan Andrés, Montávez Juan Pedro,
Project Climate and Environmental Physics: Pleistocene Earth System Evolution (pleistoCEP)
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Original article (peer-reviewed)

Journal Geoscientific Model Development
Volume (Issue) 11(6)
Page(s) 2231 - 2247
Title of proceedings Geoscientific Model Development
DOI 10.5194/gmd-11-2231-2018

Open Access

URL http://doi.org/10.5194/gmd-11-2231-2018
Type of Open Access Publisher (Gold Open Access)

Abstract

Abstract. Regional climate modelling is used to simulate the hydrological cycle, which is fundamental for climate impact investigations. However, the output of these models is affected by biases that hamper its direct use in impact modelling. Here, we present two high-resolution (2 km) climate simulations of precipitation in the Alpine region, evaluate their performance over Switzerland and develop a new bias-correction technique for precipitation suitable for complex topography. The latter is based on quantile mapping, which is applied separately across a number of non-overlapping regions defined through cluster analysis. This technique allows removing prominent biases while it aims at minimising the disturbances to the physical consistency inherent in all statistical corrections of simulated data. The simulations span the period 1979–2005 and are carried out with the Weather Research and Forecasting model (WRF), driven by the ERA-Interim reanalysis (hereafter WRF-ERA), and the Community Earth System Model (hereafter WRF-CESM). The simulated precipitation is in both cases validated against observations in Switzerland. In a first step, the area is classified into regions of similar temporal variability of precipitation. Similar spatial patterns emerge in all datasets, with a clear northwest–southeast separation following the main orographic features of this region. The daily evolution and the annual cycle of precipitation in WRF-ERA closely reproduces the observations. Conversely, WRF-CESM shows a different seasonality with peak precipitation in winter and not in summer as in the observations or in WRF-ERA. The application of the new bias-correction technique minimises systematic biases in the WRF-CESM simulation and substantially improves the seasonality, while the temporal and physical consistency of simulated precipitation is greatly preserved.
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