Spatial-temporal variability of climate indices in Chungcheong provinces of Korea: Application of graphical innovative methods for trend analysis

Climate change causes unprecedented damage in form of climate extreme events such as floods and drought, especially in the agricultural sector. Understanding the variations and trends of climate characteristics is a step toward mitigating climate-related disasters. This study investigates the annual and seasonal spatial-temporal variability of UNEP and De Martonne climate indices from 10 synoptic stations distributed homogeneously over the Chungcheong Provinces in Korea from 1974 to 2019. The spatial assessment of the variability of climate indices was conducted using the inverse distance weighting (IDW) interpolation method. The annual and seasonal trends were assessed using innovative trend analysis (ITA), while a further trend assessment on a seasonal scale was conducted using innovative polygon trend analysis (IPTA) to reveal periodic features and trend transitions. The results of the ITA were compared to the classical Mann-Kendall (MK) and Modified Mann-Kendall (MMK) trend methods. The findings revealed that the Chungcheong Provinces is a wet climate dominance on an annual scale, with a high occurrence frequency of humid to extreme humid climates. However, there are variations in the climatic classes of UNEP and De Martonne indices on the seasonal timescale and across the stations. The spatial assessment indicated the dominance of moderate climatic conditions, while the heavy climatic condition is consistent at the far-end northeast. The ITA shows significant (95% confidence level) upward trends on an annual scale at 50 and 60% of the stations in UNEP and De Martonne indices, respectively. Moreover, an increasingly significant trend dominated the summer and autumn, while spring and winter seasons exhibited significant decreasing trends. The IPTA shows a dominant transition from the increasing area in autumn to decreasing area in winter, while summer consistently transited in the increasing region at almost all the stations. Both climate indices demonstrate homogeneous and isotropic behaviors and nearly stable conditions. Furthermore, ITA and MK trend statistics indicate a good positive correlation (r > 0.50). The findings of this study are important for the ongoing climate-change-related policy in the agricultural sector in Korea.