Abstract
Abstract. Extreme precipitation (EP) is a major external agent driving various natural hazards in the Loess Plateau (LP), China. However, the characteristics of the spatiotemporal EP responsible for such hazardous situations remain poorly understood. We integrate universal multifractals with a segmentation algorithm to characterize a physically meaningful threshold for EP (EPT). Using daily data from 1961 to 2015, we investigate the spatiotemporal variation of EP over the LP. Our results indicate that (with precipitation increasing) EPTs range from 17.3 to 50.3 mm d−1, while the mean annual EP increases from 35 to 138 mm from the northwestern to the southeastern LP. Further, historically, the EP frequency (EPF) has spatially varied from 54 to 116 d, with the highest EPF occurring in the mid-southern and southeastern LP where precipitation is much more abundant. However, EP intensities tend to be strongest in the central LP, where precipitation also tends to be scarce, and get progressively weaker as we move towards the margins (similarly to EP severity). An examination of atmospheric circulation patterns indicates that the central LP is the inland boundary with respect to the reach and impact of tropical cyclones in China, resulting in the highest EP intensities and EP severities being observed in this area. Under the control of the East Asian monsoon, precipitation from June to September accounts for 72 % of the total amount, and 91 % of the total EP events are concentrated between June and August. Further, EP events occur, on average, 11 d earlier than the wettest part of the season. These phenomena are responsible for the most serious natural hazards in the LP, especially in the central LP region. Spatiotemporally, 91.4 % of the LP has experienced a downward trend in precipitation, whereas 62.1 % of the area has experienced upward trends in the EP indices, indicating the potential risk of more serious hazardous situations. The universal multifractal approach considers the physical processes and probability distribution of precipitation, thereby providing a formal framework for spatiotemporal EP assessment at the regional scale.
Highlights
Extreme precipitation (EP) is the dominant external agent driving processes such as floods, erosion, and debris flow, which have adverse impacts on human life, the social economy, the natural environment, and ecosystems (Min et al, 2011; Pecl et al, 2017; Walther et al, 2002)
Our objectives are to (1) apply the universal multifractal approach to determine a unique set of extreme precipitation threshold (EPT) for the Loess Plateau (LP) area, (2) investigate how spatial variations in EP are responsible for the severe nature of soil erosion, and (3) assess the spatiotemporal variation of EP over the LP during the period from 1961 to 2015
Notable occurrences of high EP frequency (EPF) can be seen in and around the Ziwuling Mountains in the mid-southern LP, whereas the highest frequency occurred to the east of the Fenhe Valley in the southeastern LP
Summary
Extreme precipitation (EP) is the dominant external agent driving processes such as floods, erosion, and debris flow, which have adverse impacts on human life, the social economy, the natural environment, and ecosystems (Min et al, 2011; Pecl et al, 2017; Walther et al, 2002). These impacts are especially severe in arid and semiarid areas because of the sparsity of vegetation and the fragility of the ecoenvironment (Bao et al, 2017; Huang et al, 2016). Zhang et al.: A universal multifractal approach to assessment of spatiotemporal extreme precipitation
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