青藏高原低频振荡对2013年夏季长江流域高温热浪的影响

利用1971-2013年台站逐日最高气温、平均气温站点资料和NCEP/NCAR逐日再分析资料,通过小波分析、Butterworth带通滤波、相关分析、合成分析等方法,分析了青藏高原的低频振荡特征及其对长江流域高温热浪的影响。结果表明:2013年夏季,长江中下游地区最高气温、平均气温均存在40~70d和10~20d的两个振荡周期,并且,高原季风变化存在显著的40~70d振荡周期,200hPa上空南亚高压也以40~70d周期变化为主;在40~70d的低频振荡尺度上,高原季风偏强对应600hPa从伊朗高原到青藏高原再到长江中下游地区均为低频气旋环流系统,南亚高压偏强对应200hPa高原主体为低频反气旋系统;长江中下游地区受到高原和东海地区低频系统的影响,近地面气压升高,可能导致温度上升;高原季风的低频分量增大(减小)可能导致滞后其20d的长江中下游地区温度升高(降低),而南亚高压的低频分量增加(减少)可能导致滞后其13d的长江中下游地区温度升高(降低)。

Influence of Atmospheric Low-frequency Oscillations over Qinghai-Tibet Plateau on Heatwaves in the Yangtze River Basin in Summer of 2013

Using the daily data of highest and the average temperature from 1971 to 2013 and NCEP/NCAR daily reanalysis data set, with wavelet analysis, Butterworth band-pass filtering, correlation analysis and synthetic analysis method, the low frequency oscillation of the Qinghai-Tibet plateau and its influence on high temperature heat wave in the Yangtze river basin were studied. The main conclusions are as follows: in the summer of 2013, the highest and the average temperature of the middle and lower reaches of the Yangtze river region are similar with the results based on wavelet analysis, there are two oscillation periods of 40~70d and 10~20d. The plateau monsoon has a significant 40~70d oscillation period, and the SAH over 200hPa is also dominated by a 40~70d oscillation period. In the low-frequency oscillation zone of 40~70d, when the Plateau monsoon is strong, the low-frequency cyclonic circulation system covers the Iranian Plateau, the Qinghai-Tibet Plateau, the middle and lower reaches of the Yangtze River at 600hPa. At 200hPa, when the SAH is strong, the plateau is dominated by a low-frequency anticyclone system. The middle and lower reaches of the Yangtze River are affected by the low-frequency system of the plateau and the East China Sea, and the rise of surface pressure may lead to the rise of temperature. The increase (decrease) of the low frequency component of the Plateau monsoon may lead to the increase (decrease) of the temperature in the middle and lower reaches of the Yangtze River with a lag of 20 days, and the increase (decrease) of the low frequency component of the South Asian High may lead to the increase (decrease) of the temperature in the middle and lower reaches of the Yangtze River with a lag of 13 days.