The Spatio-Temporal Change Characteristics and Impacts of Extreme Climate Events from 1961 to 2004 in Xinjiang

本文利用新疆54个气象台站1961-2004年逐日最高气温、最低气温及降水量资料，对极端温度值、极端降水指数、极端气温/降水事件的频数和强度的时空变化规律进行了系统的研究；并通过EOF分解揭示了新疆气温和降水异常的空间分布型和时间演变规律；探讨了新疆气候异常与NAO、El Nino及SO三个大气环流因子的关系；同时还对各种极端天气气候事件对新疆的影响作了初步分析。通过研究得到如下主要结论： 1.新疆最高气温的极端高值、最高气温的极端低值、最低气温的极端低值及最低气温的极端高值均呈现出上升趋势，且冬季最为显著。最高（低）气温的极端低值的增温幅度较极端高值显著，最低气温的极端高（低）值上升趋势明显高于最高气温的极端高（低）值。低温日数趋于减少；高温日数增多；炎热期长度增长；寒冷期长度缩短。 2.全疆最高气温和最低气温的极端高温事件大致存在显著的增加趋势；全疆大部分地区最高气温和最低气温的极端低温事件均有减少趋势。极端低温事件减少与极端低值的增加相对应，极端高温事件的增加与极端高值的增温相一致。 3.新疆年平均最高气温异常可分为全疆一致型、南北反位相型和东西反位相型。年平均最低气温异常可分为全疆一致型、南北反位相型和多极子型。年降水量异常可分为全疆一致型、南北差异型、东西差异型及地形影响型。 4.全疆大部分地区极端降水值和极端降水量均呈增加趋势，极端降水事件频数增加，极端降水平均强度增强，极端降水占年总降水量比例趋于增大。 5.高NAOI时，全疆大部分地区夏季最高（低）气温偏低，西部降水量减少，东部偏多。冬季北疆平均最高气温偏高，南疆偏低；全疆最低气温偏高；北疆部分地区降水量偏少，南疆偏多。 6. 厄尔尼诺现象与新疆年平均最高气温、平均最低气温的关系不明显，但与年降水量有一定的关系，N型降水厄尔尼诺年时增多，拉尼娜年时减少。 7.高SOI年，大部分地区当年平均最高气温偏低，次年偏高；当年平均最低气温偏低，次年降水量偏少。SOI与四季平均最高气温、最低气温及降水量有着不同的相关性。 8.由极端天气气候事件引发的气象灾害已成为新疆经济发展的一个制约因素。Based on 54 station records of daily maximum temperature, minimum temperature and precipitation in the period of 1961-2004, the temporal-spatial changing characteristics of extreme temperature value and the extreme precipitation index have been analyzed.The frequency and density of extreme temperature and precipitation events have also been analyzed systemically. Spatial distribution patterns and temporal evolution features of temperature and precipitation anomalies have been revealed by use of EOF decomposition. The relations between climatic anomalies in Xinjiang and three atmospheric circulation factors (NAO, El Nino, SO) have been discussed. And the influence has been made of all kinds of extreme weather or climate events to Xinjiang in the end. The main conclusion are as follows: 1. The increase trends were found in annual and seasonal extreme high value of maximum temperature, extreme low value of maximum temperature, extreme low value of minimum temperature and extreme high value of minimum temperature, especially in winter.The increase trends in the extreme low value of maximum (minimum) temperature are more remarkable than those in extreme high value.The increase trends in the extreme high(low) value of minimum temperature is more remarkable than those in extreme high(low) value of maximum temperature. Moreover, the numbers of days with daily minimum temperature lower than 0℃,-20℃ and - 30℃ display slight decrease trends; the numbers of days with daily maximum temperature above 35℃ and 37℃ show slight increase trends; the length of hot stage becomes longer and the length of algid stage becomes shorter 2. For most part of Xinjiang, the increase trends in the numbers of days with extreme high temperatures of maximum and minimum temperature exhibited increase trends basically, while the numbers of days with extreme low temperatures of maximum and minimum temperatures show significant decrease trends.The reduction of extreme low temperature events is corresponding with the increase of extreme low value while the increase of extreme high temperature events is corresponding with the increase of extreme high value. 3. The annual mean maximum temperatures anomaly distribution over Xinjiang was divided into three main modes as the first proximity: with the same temperature anomaly in the entire area, with the opposite anomalies in the south and north and in the east and west according to the EOF decomposition. The annual mean minmum temperatures anomaly distribution over Xinjiang were divided into three main modes as the first proximity: with the same temperature anomaly in the entire area, with the opposite anomalies in the south and north and multipolar mode. The annual precipitation anomaly distribution over Xinjiang were divided into four main modes as the first proximity: with the same temperature anomaly in the entire area, with the opposite anomalies in the south and north, in the west and west and terrain influence mode. 4. The extreme precipitation value, extreme precipitation quantity and the frequency of extreme precipitation events assume increasing tendencies in Xinjiang; the average intensity of extreme precipitation events increase; the proportion that extreme precipitation accounting for the annual precipitation tends to increase in majority area of Xinjiang. 5. When a high NAOI occurs, the mean maximum (minimum) temperature will experience lower temperature in majority area of Xinjiang and the precipitation is rare in the west, rainy in the east in summer.The mean maximum temperature will experience high temperature in Northern Xinjiang and Tianshan Mountain, lower in southern Xinjiang; the mean minimum temperature will be extensive warmer; the precipitation is rare in part of northern Xinjiang, rainy in southern Xinjiang in winter. 6. The relationship between El Nino and the annual mean maximum (minimum) temperature is insignificant, but is certain with annual precipitation in Xinjiang.The frequency of N mode（the annual precipitation is more in north and less in south） increases in the El Nino year and reduces in the La Nina year. 7. When a high SOI occurs, the current year mean maximum temperature will experience lower temperature and higher in next year in majority area of Xinjiang; the current year mean minimum temperature will experience lower temperature; the annual precipitation is rare in the next year. It is pointed out that there are also different correlations between the SO and the seasonal mean maximum (minimum) temperature and precipitation at different area. 8. The meteorological disasters which caused by the extreme weather/climate events have become a restriction factor to economy development in Xinjiang