Characteristics of Extreme Temperature Event and Its Response to Regional Warming in Northwest China in Past 45 Years

Using the daily maximum and minimum temperature dataset from 128 stations from 1960 to 2004 in Northwest China, daily extreme high temperature (EHT) and extreme low temperature (ELT) thresholds were determined by centesimal method for different stations at first, then yearly EHT and ELT events were counted up in different stations, and the characteristics of their spatio-temporal distribution were diagnosed at last. The study drawn following conclusions: 1) The consistent anomaly distribution characteristic was the most important mode of the EHT and ELT events in Northwest China. 2) The spatial distribution of the EHT and ELT events can be divided into five sub-regions, namely, the north of Qinghai and west of Gansu area, the north of Xinjiang area, the south of Xinjiang area, the east of Northwest China area and the south of Qinghai area; 3) The EHT events showed remarkable increasing trend in all of five sub-regions, but only in the north of Qinghai and west of Gansu area, sudden change phenomenon occurred; the ELT events showed decreasing trend in all of five sub-regions, and sudden change phenomenon occurred in Northwest China except for south of Qinghai area. 4) In all of five sub-regions the EHT events showed remarkable 12-14yr period oscillation, and the ELT event showed significant 13-15 yr and 7-8 yr period oscillation. 5) The EHT and ELT events displayed remarkable positive and negative response to regional warming of Northwest China respectively.