Homogeneous temperature and precipitation series of Switzerland from 1864 to 2000

A set of 12 homogenized monthly mean temperature and precipitation series of Switzerland for the period 1864-2000 are introduced. The standardized homogenization procedure, which has been developed and implemented at MeteoSwiss during recent years, is briefly reviewed and the inhomogeneity types, causes, magnitudes, and timings are discussed. Finally, a trend analysis is performed on each temperature and precipitation series and on a mean temperature series of Switzerland. The results are compared with findings of other studies that have examined long-term temperature and precipitation trends in Switzerland and neighbouring countries. The inhomogeneities of the Swiss temperature series are up to +/-1.6 degreesC and the precipitation adjustment factors vary between 0.5 and 1.6. Each of the 12 temperature series analysed contains several inhomogeneities that cause systematic biases in the adjustment curves. The slope of a mean temperature curve derived from the original data is underestimated by 0.4 degreesC/100 years. All precipitation series except one contain inhomogeneities, but no systematic bias is observed. The trend analysis reveals an increase in the yearly temperature series ranging from 0.9 degreesC/100 years to 1.1 degreesC/100 years at stations north of the alpine main crest and similar to0.6 degreesC/100 years at southern stations. Precipitation trends are observed at most sites north of the alpine main crest in winter and in some of the yearly series. The annual slopes vary between 7 and 10% and the winter slopes between 16 and 37%. Copyright (C) 2005 Royal Meteorological Society.