Compound Droughts and Heat Waves in China

Lei Ye,Chi Zhang,Chao Wang,Ke Shi,Zhuohang Xin

doi:10.3390/su11123270

Abstract

Droughts and heat waves both are natural extreme climate events occurring in most parts of the world. To understand the spatio-temporal characteristics of droughts and heat waves in China, we examine changes in droughts, heat waves, and the compound of both during 1961–2017 based on high resolution gridded monthly sc_PDSI and daily temperature data. Results show that North China and Northwest China are the two regions that experience the most frequent droughts, while Central China is the least drought-affected region. Significant drought decreasing trends were mostly observed Qinghai, Xinjiang, and Tibet provinces, while the belt region between Yunnan and Heilongjiang provinces experienced significant drought increasing trends. Heat waves occur more frequently than droughts, and the increase of heat wave occurrence is also more obvious. The increasing of heat wave occurrence since the 2000s has been unprecedented. The compound droughts and heat waves were mild from the 1960s to 1980s, and began to increase in 1990s. Furthermore, the significant increasing trends of the percentage of compound droughts and heat waves to droughts are observed in entire China, and more than 90% drought occurrences are accompanied by one or more heat waves in the 2010s. The results highlight the increased percentage of compound droughts and heat waves and call for improved efforts on assessing the impact of compound extremes, especially in an era of changing climate.

Highlights

Climate change is expected to cause the hydrologic cycle to speed up and intensify as warming global temperatures increase the rate of evaporation, in which many hydrological processes are deeply involved
To better understand the drought patterns over China, the annual average number of drought occurrences at the decadal level for seven regions is presented in Figure 2 and Table 1
Our results indicate that NC and NWC are the two regions that experienced the most frequent droughts, while the Central China (CC) is the least drought-affected region

Summary

Introduction

Climate change is expected to cause the hydrologic cycle to speed up and intensify as warming global temperatures increase the rate of evaporation, in which many hydrological processes are deeply involved. Estimations of the risks of climate extremes typically focus on an isolated process or variable, which is usually not capable to fully characterize the impact of extremes due to the fact that climatic variables are intrinsically interconnected. Recent studies have begun to explore trends and changes in compound extremes, such as droughts and heat waves [8,9,10], and these studies have recognized the necessity of jointly investigating climate events. Compound extremes, which are referred to as simultaneous, concurrent, or coincident extremes, are commonly defined as the occurrence of multiple events that lead to extreme impacts [11,12,13,14]

Results

Discussion

Conclusion