Homogeneity of average annual air temperature time series for Croatia

Abstract

AbstractHomogeneity of the mean annual air temperature values at 2 m above ground for 22 stations in Croatia, in the period 1961–2000, is considered. The standard normal homogeneity test (SNHT) has been applied for this purpose, detecting both abrupt and gradual linear trend homogeneity breaks. For a group of lower‐rank weather stations (poorer data quality), the results indicating inhomogeneity are sometimes difficult to explain. It has been shown that homogeneity breaks in multiannual averages are not higher than 0.5 °C, which could influence the natural trend analysis as well as some other statistical structures such as climatological normals, correlation functions or smoothed time series. Because of this, homogenization has usually to be adapted to the newest situation. On the other hand, the first principal component amplitude, describing more than 90% of the considered air temperature field variance, indicates that the spatial average of the mean annual temperature for the whole territory of Croatia is not dependent on inhomogeneities present in a particular time series. This result is in accordance with those previously obtained for Sweden and Switzerland as well as with some similar results obtained for larger continental and global scales. [‘However, Easterling and Peterson (1995a, b) found that on very large spatial scales (half a continent to global), positive and negative homogeneity adjustments in individual station's maximum and minimum temperature time series largely balance out so when averaged into a single time series, the adjusted and unadjusted trend were similar.’–cited by Peterson et al. (1998)]. Copyright © 2009 Royal Meteorological Society