Investigating the trend of extreme climatic events in South Khorasan province

In recent years, extreme events (droughts, floods, and extreme heat waves), as indicators of climate change, have received heightened attention. Increased concentration of greenhouse gases has led to global warming and significant changes in climatic extreme events pattern. In this study, 28 extreme indices proposed by a joint project between the World Meteorological Organization, the Climatic Group, the Climate Variability and Predictability Group, and the Global Research Program for Climate Change Monitoring and Detection, have been calculated from daily temperature and precipitation series of 12 meteorological stations in South Khorasan province during the period of 1992-2016. The non-parametric Mann-Kendall (MK) statistical test has been used to assess the significance of trend in extreme indices time series. The results showed a significant increasing trend in warm extreme indices and the decreasing trend for cold extreme events in most stations. Such that, the number of summer days with mean temperature above 25 degrees Celsius (SU 25) has an increasing trend in all stations. A decreasing trend was observed in cool nights (TN10P) series in most stations. There exists a high spatial variation for rainfall in the study region and no significant pattern could be observed, but in general, the trend in most stations is decreasing, for instance, the rainfall events greater than 1mm in north and central regions of the province has significantly decreased.