Abstract
Based on daily measured data from 25 stations in Xinjiang Province from 1963 to 2017, we discuss the statistical characteristics, linear trends, and temporal concentration of slight precipitation (SP) and extreme precipitation (EP) events, and consider relationships between SP and EP events and daily mean temperature. The results show that SP events contribute strongly to the total annual number of wet days, and that EP events contribute strongly to the total annual precipitation amount. In consist with the decrease in SP events and the increase in EP events over the 55-year period, the contribution of SP events to total annual number of wet days has decreased significantly while the contribution of EP events to total annual precipitation amount has increased significantly. SP event usually distributes through most months of the year, whereas EP event usually concentrates in summer (JJA). Influenced by the negative trends for SP events frequency and positive trends of EP events frequency during recent decades, the concentration degree for SP and EP events have significantly increased and decreased, respectively. Distinct differences are found between the relationships of SP events and EP events to daily mean temperature. The daily mean temperature recorded at the stations in Northern Xinjiang on days with SP events was between –35°C and +34°C, and for EP events ranged from –21°C to +30°C. Regionally averaged curves for the change in SP and EP event frequency with temperature have bimodal and unimodal distributions, respectively. Trends for daily mean temperatures and for the frequency of SP events at different temperatures agree well over nearly the entire temperature range, while trends for daily mean temperatures and for the frequency of EP events at different temperatures are not always consistent. These results will help to improve our understanding of the characteristics and variability of precipitation in arid regions within the context of climate warming.
Highlights
Significant climate responses to global warming have been observed in arid and semi-arid areas
In order to have a better understand of the warm and humid climate change and to counter the extreme climate issues in Xinjiang, such as drought in spring while flood in summer, and the coexistence of drought and flood, many studies for precipitation response to the rising temperature were conducted (Wang et al, 2012, 2013, 2017; Jiang et al, 2013; Deng et al, 2014; Yao et al, 2015). Most of these works emphasized the significant increase in extreme precipitation (EP) events and discussed its potential impacts, but less well understood and insufficient studies have been carried out regarding the slight precipitation (SP) events, a precipitation type that account for large proportions in total annual wet days in Xinjiang province (Fu et al, 2008; Liao et al, 2012) and have large importance in arid lands
To better understand changes in SP and EP events at stations across Northern Xinjiang, we looked at linear trends in the contribution of SP and EP events to the total number of wet days and total annual precipitation amounts
Summary
Significant climate responses to global warming have been observed in arid and semi-arid areas. Accompanied with the warm and humid climate tendency in Xinjiang Province, apart from the significant upward trends for the frequency of extreme precipitation events, obvious increase in small precipitation events and total number of annual wet days were observed in both the relatively earlier works (Zhai et al, 2005; Qian et al, 2007; Fu et al, 2008) and those recent ones (Jiang et al, 2013; Wang et al, 2013; Deng et al, 2014; Zhou et al, 2015) These changes conflict with the “wetget-wetter” (dry-get-drier) theory, and cannot be well explained by the conclusion in Trenberth et al (2003) too. It is worth considering whether the transition from manual to automatic observations in Xinjiang could be a cause of inhomogeneity in the precipitation data, especially for SP
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