A Universal Multifractal Approach to Assessment of Spatiotemporal Extreme Precipitation over the Loess Plateau of China

Source abstract

Abstract. Extreme precipitation (EP) is a major external agent driving various natural hazards in the Loess Plateau (LP), China. Yet, the characteristics of 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 EPTs range from 17.3 to 50.3 mm/d while the mean annual EP increases from 35 to 138 mm from northwest to southeast LP. Further, EP frequency (EPF) has historically spatially varied from 54–116 days, 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 scare, and get progressively weaker as we move towards the margins (similarly with EP severity). An examination of atmosphere circulation patterns indicates that the central LP is the boundary where tropical cyclones reach furthest into inland China, resulting in the highest EP intensities and EP severities being in this area. Under the control of the East Asian monsoon, precipitation from June to September accounts for 72 % of the total amount, while 91 % of the total EP events are concentrated in June to August. Further, EP events occur, on average, 11 days 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 region. Spatiotemporally, 91.4 % of the LP has experienced a downward trend of precipitation, while 62.1 % of the area has experienced upward trends of the EP indices, indicating the potential risk of more serious hazardous situations.