SST and circulation trend biases cause an underestimation of European precipitation trends
- 875 Downloads
Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in north-western Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern Europe in winter. An investigation of precipitation trends in two multi-model ensembles including both global and regional climate models shows that these models fail to reproduce the observed trends. In many regions the model spread does not cover the trend in the observations. In contrast, regional climate model (RCM) experiments with observed boundary conditions reproduce the observed precipitation trends much better. The observed trends are largely compatible with the range of uncertainties spanned by the ensemble, indicating that the boundary conditions of RCMs are responsible for large parts of the trend biases. We find that the main factor in setting the trend in winter is atmospheric circulation, for summer sea surface temperature (SST) is important in setting precipitation trends along the North Sea and Atlantic coasts. The causes of the large trends in atmospheric circulation and summer SST are not known. For SST there may be a connection with the well-known ocean circulation biases in low-resolution ocean models. A quantitative understanding of the causes of these trends is needed so that climate model based projections of future climate can be corrected for these precipitation trend biases.
KeywordsEurope Precipitation Trends Climate models Observations Uncertainty
The research was supported by the Dutch research program Knowledge for Climate. MC was partially supported by the NERC Changing Water Cycle PAGODA Project.
- Annan J, Hargreaves J (2010) Reliability of the CMIP3 ensemble. Geophys Res Lett. doi: 10.1029/2009GL041994
- Ashfaq M, Skinner C, Diffenbaugh N (2010) Influence of SST biases on future climate change projections. Clim Dyn, 1–17, doi: 10.1007/s00382-010-0875-2
- Hegerl G, Zwiers F (2011) Use of models in detection and attribution of climate change. Wiley Interdisciplinary Reviews. Clim Change. doi: 10.1002/wcc.121
- Hudson D, Jones R (2002) Regional climate model simulations of present-day and future climates of Southern Africa. Technical note 39, Hadley Centre for Climate Prediction and ResearchGoogle Scholar
- Rummukainen M, Bergstrom S, Persson G, Rodhe J, Tjernstrom M (2004) The Swedish regional climate modelling programme, SWECLIM: a review. Ambio 33:176–182. http://highwire.stanford.edu/cgi/medline/pmid;15264594 Google Scholar
- Schneider U, Fuchs T, Meyer-Christoffer A, Rudolf B (2010) Global precipitation analysis products of the GPCC. Technical report, Global Precipitation Climatology Centre (GPCC), Deutscher Wetterdienst, Offenbach, Germany. http://gpcc.dwd.de
- van der Linden P, Mitchell JFB (eds) (2009) ENSEMBLES: climate change and its impacts: summary of research and results from the ENSEMBLES project. Met Office Hadley Centre, Exeter, pp 160Google Scholar