Articles | Volume 19, issue 6
Nonlin. Processes Geophys., 19, 623–633, 2012
Nonlin. Processes Geophys., 19, 623–633, 2012

Research article 13 Nov 2012

Research article | 13 Nov 2012

Conditioning model output statistics of regional climate model precipitation on circulation patterns

F. Wetterhall1,2, F. Pappenberger1,3, Y. He4, J. Freer5, and H. L. Cloke1,6 F. Wetterhall et al.
  • 1European Centre for Medium Range Weather Forecasts, Reading, UK
  • 2Department of Geography, King's College London, London, UK
  • 3Hohai University, Nanjing, China
  • 4Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, UK
  • 5School of Geographical Sciences, University of Bristol, UK
  • 6Department of Geography & Environmental Science and Department of Meteorology, University of Reading, UK

Abstract. Dynamical downscaling of Global Climate Models (GCMs) through regional climate models (RCMs) potentially improves the usability of the output for hydrological impact studies. However, a further downscaling or interpolation of precipitation from RCMs is often needed to match the precipitation characteristics at the local scale. This study analysed three Model Output Statistics (MOS) techniques to adjust RCM precipitation; (1) a simple direct method (DM), (2) quantile-quantile mapping (QM) and (3) a distribution-based scaling (DBS) approach. The modelled precipitation was daily means from 16 RCMs driven by ERA40 reanalysis data over the 1961–2000 provided by the ENSEMBLES (ENSEMBLE-based Predictions of Climate Changes and their Impacts) project over a small catchment located in the Midlands, UK. All methods were conditioned on the entire time series, separate months and using an objective classification of Lamb's weather types. The performance of the MOS techniques were assessed regarding temporal and spatial characteristics of the precipitation fields, as well as modelled runoff using the HBV rainfall-runoff model. The results indicate that the DBS conditioned on classification patterns performed better than the other methods, however an ensemble approach in terms of both climate models and downscaling methods is recommended to account for uncertainties in the MOS methods.