The application of piecewise ITA method in Oxford, 1870-2019

Abstract

In this study, the trends, stabilities of temperature, and rainfall data have been analyzed in detail for hydrometeorology time series recorded since 1870 in Oxford city in England. The innovative trend analysis (ITA) method has been used to identify and analyze the piecewise trends and stabilities of the selected time series. To compare the results, the modified Mann-Kendall (MMK) and Sen's slope (SS) methods have been applied to each series as a piecewise ITA application. To obtain reliable and objective conclusions, +/- 5% and +/- 10% trend percentage lines have been considered in the application of the ITA method. The piecewise ITA method provides more detailed information in this study, compared to the studies in the literature such as the MMK. Identification of trends that implies climate change is taken into consideration by the ITA approach for future design purposes. In this study, the available time series with a record length of 150 years has been divided into sub-series of 30 years considering the last 30-year period in which climate change began to be discussed due to its significant effects. As a result, when the trends of 150 years are examined for the different partial series, it is seen that the temperature increase in the 1990-2019 period is much higher than the past 120 years. The highest average rainfall occurred in the 1990-2019 and 1900-1929 periods, and their amounts are nearly similar.