资源环境科技发展态势分析平台

In recent years, extreme droughts have been frequent and widespread, and understanding the spatiotemporal variations in drought events in China plays an important role in drought risk management. In this study, using monthly meteorological data at 618 stations, we computed the Standardized Precipitation Evapotranspiration Index with potential evapotranspiration based on the Penman-Monteith equation (SPEI_PM) for drought assessment. Furthermore, we analysed the trend, affected area, frequency and duration of drought in China over the period of 1960-2014 by the piecewise linear regression method (LRM) and Mann-Kendall (MK) method. The results showed that (a) the slight wetting trend reflected during 1960-2014 by the SPEI_PM (0.03/10a (p > .05). This trend was allocated to most parts of northern and southeastern China and was prone to arrive in winter. In contrast, the most significant drying trend was in the Loess Plateau and Yunnan-Kweichow Plateau. (b) The turning point (TP) year of drought trend was 1993. The SPEI_PM was increased in most parts of northern China before 1993 according to the LRM and MK method. However, it decreased after 1993, especially in the south and northwest of China; (c) Over the past 55 years, the areas affected by drought decreased at a rate of -1.23%/10a (p < .05). In detail, these areas decreased at a rate of -3.41%/10a before 1993 (p < .05) and increased at a rate of 2.71%/10a after 1993 (p > .05). (d) The drought frequency in most parts of China was between 15 and 20 during 1960-2014. Furthermore, compared with that in 1960-1977, the drought frequency was decreased in 1978-1995 and then increased in 1996-2014. These findings suggested that the long-term trend in drought events during 1960-2014 was not significant in China. However, the severity, affected area and frequency of droughts increase after 1993. These results allowed us to understand the changes in the drought across China over the last 55 years, which is important for guiding relevant agricultural activities.