Recent changes in extreme precipitation and drought over the Songhua River Basin, China, during 1960–2013

Abstract

Based on ten indices of extreme precipitation and one drought index (composite index, CI), the trends in extreme events were investigated using a Mann-Kendall non-parametric method at 39 stations in the Songhua River Basin (SHB) during 1960-2013. The regionally averaged wet-day precipitation (PRCPTOT) increased at a rate of 1.65 mm/year (R 2 = 0.28, P = 0.13), in which 82% of the stations experienced increases, but only 4 stations showed significant positive trends. The annual R95 and R99 exhibited slight upward trends at rates of 1.37 (R 2 = 0.21, P = 0.27) and 1.28 mm/year (R 2 = 0.23, P = 0.23) over the last 54 years; however, there were not significant trends in R95 and R99 at the 0.05 level. PRCPTOT, R95 and R99 showed similar spatial trends, in which positive trends mainly occurred in the northern and southeastern basins. The trends in the maximum 1-day precipitation (RX1day) and maximum 5-day precipitation (RX5day) do not show a prevalent trend (approximately 50% of the stations have a positive trend and the remaining stations have a negative trend). The simple daily intensity index (SDII) significantly decreased at an annual rate of 0.02 mm/d during 1960-2013 (R 2 = 0.66, P b 0.01); spatially, 49% of the stations experienced statistically significant decreases at the 0.05 level based on the Mann-Kendall non-parametric test. The regionally averaged heavy (R10mm) and very heavy precipitation days (R20mm) and consecutive wet days (CWD) showed no significant trends during the past 54 years; however, several individual extreme precipitation events, such as the flood of 1998 in the SHB, were well detected by these indices. The regionally averaged consecutive dry days (CDD) significantly increased (R 2 = 0.79, P b 0.01) at a rate of 0.22 days/year from 1960 to 2013. All of the stations exhibited statistically significant increases in CDD, excluding the Tongyu station in the western basin. The monthly RX5day values were highest in summer, from June to August, in the SHB; a peak occurred in July (67.5 mm) in the SHB during 1960-2013. The CI peaked in July, with the highest value of 0.2 in the SHB during 1960-2013. However, the two lowest CI values occurred in spring and fall, with values of −0.56 and −0.41, respectively. During April and May, when most of the spring drought events occur, a prevalent trend does not exist; moreover, almost no stations have statistically significant CI increases. In August and September, respectively 79% and 97% of the stations exhibited a CI negative trend, but only 2 and 6 stations showed significant decreases at the 0.05 level. The increasing extreme climate events present a challenge for local water resources management.

Rising Precipitation Extremes across Nepal

“…This finding is consistent with previous studies of Shrestha et al [32] and Sigdel and Ma [104] over Koshi basin of Nepal. A similar increase in CDD has also been reported for the Songhu River basin in China [108] and across Bangladesh [109], as CDD is mostly related to the large-scale weather systems rather than localized systems [68].…”

Recent changes in daily climate extremes in an arid mountain region, a case study in northwestern China’s Qilian Mountains

“…Consequences for society have risen, and included direct or indirect life and property losses due to extreme climatic events 11 . Consequences of extreme climate events for natural systems included extension of the growing season 3 , increased incidence of spring drought events 12 , and adverse effects on soil erosion processes 13 . Thus, a detailed analysis of the spatial and temporal characteristics of temperature and precipitation extremes is essential for establishing ecosystem management strategies for a changing climate.…”

Nonstationary modeling of extreme precipitation in China

“…At national or regional scale, the changes of precipitation extremes were also extensively studied, and significant trends in precipitation extremes were detected in the United States, Australia, Goswami et al, 2006;Fu et al, 2010;Boccolari and Malmusi, 2013;Cino et al, 2014;Limsakul and Singhruck, 2016;Singh and Goyal, 2016). In China, significant trends in precipitation extremes have also been detected with apparent regional differences (Zhai et al, 2005;Qian and Qin, 2008;Xu et al, 2011;You et al, 2011;Deng et al, 2014;Song et al, 2015;Sun et al, 2016). Under the background of climate change, it is worthy to study precipitation extreme and assess its adverse influence, because extreme precipitation events are considered as the major causes of severe floods in China (Zhai et al, 2005).…”