我国江南夏季极端高温季节内变化特征初探

利用1979~2013年逐日最高温度观测资料，通过Butterworth带通滤波和功率谱分析等方法，分析我国江南夏季极端高温季节内变化特征。结果表明：7月中旬至8月中旬，江南地区（110°E ~125°E，22.5°N~30°N）为高温日数高值区，高温日数存在季节内振荡信号。功率谱结果表明该地区日最高温度呈现出10~25 d的季节内振荡周期；在以10~15 d和20~25 d周期为主的低频变化典型年份（1989和1993年）中，影响系统与副热带高压并无直接联系，对流层中高层45°N存在2~3波的纬向波列，该波列的移动与传播可能与温度的低频变化有关。

Preliminary Analysis of Intraseasonal Oscillation of Summer Extreme Daily Temperature in China

Based on the daily observation data during 1979-2013, the characteristics of internal oscillation in summer extreme high temperature in southern of the Yangtze river were further discussed. By using Butterworth filter and power spectrum methods, results show that: From the middle of July to the middle of August, the high value center moves into southern of the Yangtze river(110°-125°E,22.5°N-30°N) and averaged hot days beyond 95% threshold show oscillation feature. Result of Power spectrum indicates daily maximum temperature presents the characteristics of intraseasonal variation in 10-25d. The impact system is not directly related to the subtropical high in the typical low frequency year(1989 and 1993). On the middle and high troposphere, the geopotential height presents 2 to 3 waves with the obvious intraseasonal oscillation features(10-15 day and 20-25day). The motion and propagation of the wave may be related to the low frequency variation of temperature.