非ENSO事件次年大西洋海温异常对夏季青藏高原大气热源准双周低频活跃度的影响

The Possible Influence of Atlantic Sea Surface Temperature Anomalies for Low-Frequency Intensity over Qinghai-Tibetan Plateau during Summer of No-ENSO Events Following Years

夏季青藏高原大气热源准双周低频活动明显,并存在显著年际变化。利用NCEP/NCAR再分析资料,定义夏季高原区域内大气热源准双周分量的标准化方差为该年的低频活跃度,其对中国东部天气变化有一定指示意义,高原低频活跃度较大时,中国东部夏季存在"旱涝并存"和"旱涝急转"现象。通过诊断分析,发现多个海温关键区都对低频活跃度有一定影响,不同年份的主导影响因素不同。ENSO事件次年,主要是太平洋海盆区域内海温异常影响青藏高原夏季低频活跃度;非ENSO事件次年,大西洋海盆区域内的三极型海温异常起主要影响作用。在非ENSO事件次年,前期冬春季大西洋三极型海温异常能够激发出异常的类EU波列,影响高原区域上空的大气环流。在同样的触发机制下,正位相时的类EU波列有利于云辐射反馈的发展,负位相时的类EU波列不利于云辐射反馈的发展,从而影响夏季高原热源低频活跃度。

Quasi-biweekly oscillation of atmospheric heat source （（Q1） ） over Qinghai-Tibetan Plateau （QTP）is significant according to many previous studies, and it can be used as a predictor of the climate change in Eastern China. In quasi-biweekly oscillation active year, Eastern China is likely to experience a fast conversion from flood to drought or from drought to flood. On the basis of NCEP/NCAR reanalysis data and daily （ Q1 ） empirical orthogonal function results, standardized variance was defined as the index of Low-frequency intensity （ITPI） over QTP to describe the low-frequency activity. The main results showed that there is an annual variance in the low-frequency activity intensity, Pacific Ocean and Atlantic Ocean can both take effects on quasi-biweekly oscil- lation over QTP, the main influential factor is different in different years. During the following year of the ENSO events, the tropical pacific sea surface temperature anomaly is the key factor; During the following year of the No-ENSO events, the Atlantic Ocean triple anomaly sea surface temperature is the dominant factor which can motivate the anomaly EU wave train thus affecting the atmospheric circulation. Under the same trigger condition, the positive phase of the EU wave train is in favor of the development of cloud radiant feedback and then influ- ence the low-frequency intensity, While the negative phase of EU wave train can suppress the development of cloud radiant feedback which cause weak Quasi-biweekly oscillation of atmosohere heat source over OTP.