夏季青藏高原热源低频振荡对我国东部降水的影响

利用NCEP/NCAR逐日再分析资料及长江中下游降水资料, 诊断和分析了长江中下游地区旱年1978年、涝年1999年青藏高原东部大气热源与降水季节内振荡的关系, 并着重讨论了青藏高原低频热力过程的经、纬向传播, 结果表明:1978年夏季青藏高原东部大气热源存在10~20 d周期为主的振荡, 交叉谱分析表明:青藏高原东部热源与长江中下游降水在10~20 d频段存在显著相关, 且青藏高原激发的周期为10~20 d的低频振荡热源在纬向上呈现出驻波形式; 1999年夏季青藏高原东部热源存在30~60 d周期为主的振荡, 热源与长江中下游降水在30~60 d频段存在显著相关。

Effect of Summer Heat Source Low-frequency Oscillation over the Tibetan Plateau on Precipitation in Eastern China

The relation between the atmospheric heat source (AHS) over the eastern Tibetan Plateau (TP) and rainfall intraseasonal oscillation is investigated using daily NCEP/NCAR reanalysis and observed rainfall data of the middle and lower reaches of the Yangtze River during the year 1978 of drought and 1999 of flood. The propagation of low-frequency oscillation AHS over the eastern TP are studied too. The results show that the 10—20 day oscillations have important contributions to AHS over the eastern TP in summer of 1978, and 30—60 day oscillations play an important role in AHS over the eastern TP in summer of 1999. AHS over eastern TP takes on a form of intraseasonal oscillation not only in 1978 but also in 1999. And a remarkable correlation is found between AHS over the eastern TP and rainfall in the Yangtze River valley at intraseasonal oscillation period of time by cross spectrum analysis. In addition, based on 10—20 days and 30—60 days filter curves of AHS over the eastern TP in summer of 1978 and 1999, low-frequency AHS at period of 10—20 days over the eastern TP appears standing wave in zonal direction in 1978, but low-frequency AHS at period of 30—60 days over the eastern TP moves eastward to middle and lower reaches of the Yangtze River.