Trend Slope Risk Charts (TSRC) for piecewise ITA method: an application in Oxford, 1771–2020

In this study, the 250-year precipitation data, and the 200-year temperature data belonging to the Radcliffe station located in Oxford city of England have been analyzed. The piecewise trends, their magnitudes, and stabilities have been determined in the study through modified Mann–Kendall (m-MK), Sen’s slope (SS), and Innovative Trend Analysis (ITA) methodologies. This study is mainly proposed to suggest a new approach for the trend slope (magnitude) based on the ITA with Trend Slope Risk Charts (TSRC). The numerical evaluation of the trends obtained through the ITA graphs has been made for the first time via TSRC. The average trend magnitudes have been calculated for 50% risk level by forming the Cumulative Distribution Function (CDF) charts of the trend increase (or decrease) percentages to define the trend magnitudes over a single magnitude for the ITA methodology. The experts can find a chance with the TSRC to evaluate in detail the trend magnitudes for different numerical values. The m-MK methodology regarding total annual precipitation data emphasizes that there is no trend in general except for the three combinations. Nonetheless, there are trend increases in nine combinations, and partial trend decreases in two charts except for the 1871–1920 and 1971–2020 periods, according to the ITA methodology. On the other hand, the trend increases for five of the six combinations that are formed to determine the piecewise trends of the annual mean temperature data, and no trend evaluation for one of them is nearly similar for the m-MK and ITA methodologies. Finally, the differences between trend magnitudes are calculated through two different methodologies that have been discussed in detail within the scope of the study.