关键词: 多灾种, 干旱, 热浪, 复杂网络, 秦岭南北

Abstract:

Modeling the processes of multi-hazard interaction could provide a pathway for a better understanding of the question how to identify and characterize the interaction of natural hazards and what is the possible cumulative or amplification effect where a hazard triggered or combined secondary hazards, which would help scientists to understand multi-hazard cause even damage to the social-ecological system. Based on the daily observations of 72 meteorological stations released by the National Meteorological Information Center of China, this study focuses on the spatiotemporal variation in concurrences of droughts and heat waves in the south and north of Qinling Mountains region for the period of 1960-2016 by using geographical analysis, wavelet conference, complex networks and other statistical techniques. Specifically, we finished the prospective transform from bipartite to single-point network and the modification in the spatiotemporal network rules for multi-hazards, which enriched the traditional research paradigm to investigate changes in concurrent of multi-hazards under the global warming. The results showed that: (1) The wet-dry pattern in the south and north of Qinling Mountains region has switched from the dominant flooding in the 1980s to continuous droughts. Meanwhile, the increasing shift of heat waves occurred after the depression or hiatus process during 1998-2010. Severe droughts and heat waves concurrences have become frequent and higher risk of multi-hazards have increased more than single hazard in recent years. (2) Investigation reveals there is synchronous variation between the concurrent droughts and heat waves, and the relationship shows different periodicity in different periods between 1970 and 2017. A statistically significant high-power region is evidently found from the 1970s to the 1980s at the shortest timescales, i.e. 4-8 years, with droughts and heat waves decreasing simultaneously, and then the weaker correlation is observed until the early 1990s. High-power regions are also observed during 1995-2002 and 2012-2017 from quasi-decadal to the interannual timescales, i.e. 2-4 years, which show a substantial increase in concurrent droughts and heatwaves across the study region. (3) Spatially, Guanzhong basin and Hanjiang river basin are two specific regions prone to concurrent of droughts and heat waves, while the cold spots of multi-hazard are observed in the Jialing river basin, the middle part of south piedmont of Qinling Mountains and the region near Danjiangkou reservoir. (4) Here, the multi-hazard approaches framework is provided to analyse the effects of concurrent and compound extremes. In particular, spatiotemporal analysis can be used to understand the background of multi-hazard and provide some basic evidences about the interaction of natural hazards. To quantify the presence of scale-dependency in the relationship of droughts and heat waves, wavelet coherence is used from a nonstationary perspective. Finally, the spatiotemporal network for multi-hazard could explain the ‘burst’ phenomena of multi-hazard, i.e. the spatiotemporal distribution of concurrent droughts and heat waves is best described by power lows, which are neither regular nor completely random.

Key words: multi-hazard, drought, heat wave, complex network, south and north of Qinling Mountains region