Abstract
Abstract. Extreme precipitation events are major causes of severe floods and droughts worldwide. Therefore, scientific understanding of changing properties of extreme precipitation events is of great scientific and practical merit in the development of human mitigation of natural hazards, such as floods and droughts. Wetness and dryness variations during 1961–2008 in Xinjiang, a region of northwest China characterised by an arid climate, are thoroughly investigated using two extreme precipitation indices. These are annual maximum consecutive dry days (CDD) and annual maximum consecutive wet days (CWD), based on a daily precipitation dataset extracted from 51 meteorological stations across Xinjiang. As a result, we present spatial distributions of mean annual CDD and mean annual CWD and their trends within the study period. The results indicate that: (1) CDD maximize in the Taklimakan and Turban basins of southeast Xinjiang, while minima are found in the Tianshan Mountains and the Ili river valley of northwest Xinjiang. On the contrary, the longest CWD are observed in northwest Xinjiang and the shortest in the southeast part of the region. (2) On an annual basis, CWD temporal variability shows statistically positive trends and a rate of increase of 0.1d/10a. CDD temporal variability shows statistically negative trends and a rate of decrease of 1.7d/10a. (3) Goodness-of-fit analysis for three candidate probability distribution functions, generalised Pareto distribution (GPD), generalised extreme value (GEV) and Gumbel, in terms of probability behaviours of CDD and CWD, indicates that the GEV can well depict changes of CDD and CWD. (4) The CDD and CWD better describe wet and dry conditions than precipitation in the Xinjiang. The results pave the way for scientific evaluation of dryness/wetness variability under the influence of changing climate over the Xinjiang region.
Highlights
Changes in the frequency or intensity of extreme weather and climate events profoundly impact both human society and the natural environment (Easterling et al, 2000; Zhang et al, 2009, 2010b)
The consecutive dry days (CDD) and consecutive wet days (CWD) time series were assessed using daily precipitation data from 51 meteorological stations provided by the China National Meteorological Service, for the period 1961–2008
We use the generalised extreme value (GEV) statistical distribution function to fit the output of CDD/CWD for different return periods and map spatiotemporal distributions of CDD and CWD for different return periods, using all data from the selected 51 stations
Summary
Changes in the frequency or intensity of extreme weather and climate events profoundly impact both human society and the natural environment (Easterling et al, 2000; Zhang et al, 2009, 2010b). Zhang et al.: Changes in annual maximum number of consecutive dry and wet days big river valleys since the 1990s Both flood and geological disasters have increased as a consequence of the increase in concentration of intense precipitation events (e.g., Zhang et al, 2008). Increasing and intensifying weather extremes, such as with precipitation, will further increase the sensitivity of the ecological environment to climate changes, changes in precipitation. This is the major motivation for the current study. We believe that the current study is necessary for understanding precipitation changes and possible implications for flood and drought changes in the study region, under the impacts of a changing climate
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