2.3. Methods
2.3.1. Trend detection
We analyze and discuss the extreme precipitation over the LP during the period from 1979 to 2018 by using the Mann-Kendall test and the Sen’s slope estimator (Hamed 1998). The Mann-Kendall test is used to detect the significance of the change trend at each grid point. In this study, there are 13,500 grid points over the LP in the CMFD to be tested. At the 0.05 significance level, it will yield 675 (13,500 × 0.05) grid points where the significance cannot be determined, which is too high to be acceptable. Benjamini and Hochberg (1995) proposed the false discovery rate (FDR) procedure to apply the multiple Mann-Kendall tests to adjust the significance level and control the proportion of falsely rejected null hypotheses relative to the total number of rejected hypotheses.
The Sen’s slope is applied to estimate the linear trend during 1979 to 2018 for each grid point (Sen and Kumar 1968). A positive slope value indicates an increasing or upward trend in the time series, while a negative value reveals a decreasing or downward trend. Similarly, zero indicates no trend.