西北地区夏季极端高温异常特征及其成因

The characteristics and causes of extremely high temperature events in summer in Northwest China

利用全国753站1961—2010年的夏季最高气温资料,根据百分位值法定义了不同台站逐日极端高温阈值,并统计了每年每站发生极端高温事件的频次以及极端高温的强度分布,然后对极端高温事件发生频次进行了时空特征的诊断分析.在对西北地区夏季极端高温异常特征研究的基础上,分析了西北地区极端高温事件异常偏多时的大气环流异常特征.结果表明:整体一致性异常分布是西北地区极端高温事件发生频次的主要空间模态.西北地区极端高温事件发生的频次呈增加趋势,而强度则表现为减弱的趋势.当极端高温频次发生偏多时,西北地区被一个高压脊所控制,副高偏北偏强,南亚高压偏北偏西;当极端高温频次发生偏少时,西北地区上空高压脊减弱,副高偏西偏南,南亚高压偏南偏东.

By using the daily summer highest temperature data of 753 stations in China from 1961 to 2010, according to a value method to define the percentage of different stations daily extremely high temperature threshold value, and to estimate the yearly extreme high temperature event frequency of different stations, then to diagnose their spatial-temporal characteristics analysis. In addition, on the basis of the study of the northwest summer extreme high temperature anomaly characteristics, the atmospheric circulation anomalies of large-scale extreme high temperature events in this area were analyzed. The results show that extreme high temperature strength and frequency of the events are in the increasing trend, and north-south difference is bigger, when extremely high intensity is bigger, the extremely high temperature frequency is relatively small. Consistent anomaly distribution character is the main spatial model of annual extreme high temperature event frequency in northwest China. When extreme high temperature frequency happen when slant, northwest area is controlled by a ridge, the subtropical high north by strong, the South Asia high pressure move to north. And when extreme high temperature frequency happen partial for a little time, over the northwest ridge is abate, the subtropical high south west, southeast of the South Asia high slant.