Asymmetric diurnal temperature change in the Alpine Region

Abstract

By now there is general agreement that the annual mean temperature of earth's surface has increased during the last century. Recently, it has become obvious that this warming is quite inhomogeneous in various respects. Besides the spatial and seasonal variability of the temperature trend a diurnal asymmetry of increase has been observed. In large continental regions the annual mean of the daily minimum temperature has increased noticeably faster than the annual mean of the daily maximum. The same behaviour is found in the present study for low‐lying stations in Central Europe. However, data from mountain top stations show a similar increase for both minimum and maximum of daily temperatures. No diurnal asymmetry was observed for these stations. The good agreement of the time series from different mountain stations leads us to believe that the observed trends of minimum and maximum temperature are not caused by particular local influences or observation errors. An analysis of monthly and seasonal means shows that most of the warming took place in fall.