The Novelty of Extreme Natural Drought Trend Using the Statistical Approach

This study presents a method to estimate the trend of natural drought. The trend was evaluated based on the natural drought index from 1981 to 2016. Total of 6 types of Mann-Kendal models and regression models was utilized to explore the trend of natural drought for whole South Korea. The spatial characteristic of natural drought was analyzed with zonal statistical model. Various spatial statistics such as mean, variance, and extreme was investigated to find the spatial change at each zone. In addition, diverging temporal scale monthly, seasonally, and annually trend of drought was analyzed. Results show monthly temporal scale of mean zonal NDI values which is increasing or trend drought decreasing. Because the smaller NDI values, the more severe drought is. The variance zonal drought is increasing. The extreme drought is increasing in 1- and 6-months temporal scales of NDI. In the west season (summer), drought has an increasing trend. For annual temporal scale, drought has an increasing trend in the North-East of South Korea. In short, the integrated approach of regression model and geo-statistical model gives the comprehensive estimate of natural drought at various temporal scales.