Homogeneity of Climate Series

Abstract

Analyses of homogeneity of climate series and correction of heterogeneous series were undertaken in order to avoid making incorrect conclusions about climate change in Poland. The climate series homogenisation procedure was typically carried out in several stages: (1) collecting information on the history of meteorological stations (metadata), especially on significant changes in their location and measurements methods; (2) selecting the test for homogeneity control, calculating values of the test, selecting series with test values exceeding the specified critical level; (3) correction of non-homogeneous series; (4) recheck of the revised series. The correction of the climatic series analysed for the purposes of this book was carried out using various methods, specific to the climate element analysed. The most common was the relative and absolute Alexandersson test (Standard Normal Homogeneity Test, SNHT). The most common reasons for breaking the homogeneity of the climatic series were a significant change of station location and a change of the measuring instrument. However, in many cases, the cause of the series’ heterogeneity is not clear.