Seasonal and Annual Trends of Temperature and Precipitation within 1951/1971-2007 in South-Eastern Styria, Austria

Abstract

This work investigates seasonal and annual trends of temperature and precipitation from 1951/1971 to 2007 in the south-eastern part of Styria, Austria. Linear trends are calculated by least squares regression and analyzed for single station records and two different area-average time series. The focus area is represented by a regional mean and the two single stations Bad Gleichenberg and Gleisdorf. The regional mean over the focus area is calculated on the basis of seventeen stations in total previously tested by the standard normal homogeneity test. Changes in south-eastern Styria are compared with the urban station Graz University and with trends on a larger scale by the supra-regional mean over a greater territory north-east of the Alpine crest. In addition, some information regarding the sensitivity of linear trends is briefly discussed. The results reflect the warming in the 20 th century and its acceleration since the 1950s and, in particular, since the 1970s. In the period from 1971 to 2007, significant trends are detected on annual and seasonal scales, except for winter temperatures. Similar trends are observed in spring and autumn (∼1.8 °C) but the maximum increase occured in summer (∼2.5 °C). For precipitation, annual data as well as the summer and winter seasons show a decreasing tendency from 1951 to 2007 and from 1971 to 2007. Although spring and autumn conditions are characterized by a much higher spatial variability, the regional mean over the focus area indicates an increase from 1971 to 2007. The findings of the present study illustrate south-eastern Styria as a region of high sensitivity to global warming. In particular since the 1970s, the changes in temperature and precipitation are an enhanced reflection of the large-scale trends.