Dynamic Variability in Daily Temperature Extremes and Their Relationships with Large-scale Atmospheric Circulation During 1960-2015 in Xinjiang, China

Climate changes are likely to increase the risk of numerous extreme weather events throughout the world. The objectives of this study were to investigate and analyze the temporal-spatial variability patterns of temperature extremes based on daily maximum (TX) and minimum temperature (TN) data collected from 49 meteorological stations in Xinjiang of China during 1960-2015. These temperature data were also used to assess the impacts of altitude on the temperature extremes. Additionally, possible teleconnections with the large-scale circulation pattern (the El Nino-Southern Oscillation, ENSO and Arctic Oscillation, AO) were investigated. Results showed that all percentile indices had trends consistent with warming in most parts of Xinjiang during 1960-2015, but the warming was more pronounced for indices derived from TN compared to those from TX. The minimum TN and maximum TX increased at rates of 0.16 degrees C/10 yr and 0.59 degrees C/10 yr, respectively during 1960-2015. Accordingly, the diurnal temperature range showed a significant decreasing trend of -0.23 degrees C/10 yr for the whole study area. The frequency of the annual average of the warm events showed significant increasing trends while that of the cold events presented decreasing trends. Over the same period, the number of frost days showed a statistically significant decreasing trend of -3.37 d/10 yr. The number of the summer days and the growing season showed significant increasing trends at rates of 1.96 and 2.74 d/10 yr, respectively. The abrupt change year of each index was from the 1980s to the 1990s, showing that this periodic interval was a transitional phase between cold and warm climate change. Significant correlations of temperature extremes and elevation included the trends of tropical nights, growing season frequency, and cold spell duration indicator. This result also indicated the clear and complex local influence on climatic extremes. In addition, the relationship between each index of the temperature extremes with large-scale atmospheric circulation (ENSO and AO) demonstrated that the influence of ENSO on each index of the temperature extremes was greater than that of the AO in Xinjiang.