The Wave Train Characteristics of Teleconnection Caused by the Thermal Anomaly of the Underlying Surface of the Tibetan Plateau. Part Ⅰ: Data Analysis

探讨了前期青藏高原下垫面热力结构异常对后期长江中下游地区降水的影响。通过资料分析揭示出长江中下游地区夏季降水异常前期冬、春季青藏高原下垫面三维热力结构强信号特征,即长江中下游夏季旱涝前期高原南部和北部各层次的地温距平呈反位相分布。从地面0cm到地下320 cm的地温距平分布为:涝年高原偏南部(30°N以南)为正,中部和北部(30°N以北)为负,旱年时相反。其中地温距平的大值区在 40 cm到160 cm层之间。同时揭示了北半球环流型对青藏高原下垫面热力异常可能产生遥响应,并形成季尺度低频波的传播,从而影响长江中下游地区后期的降水,反映了遥相关是区域性旱涝形成的一个动力机制。资料分析结果表明前期青藏高原下垫面三维热力结构异常是后期长江中下游地区降水异常的重要原因之

The wave train characteristics of teleconnection caused by the thermal anomaly of the underlying surface of the tibetan plateau. part i: data analysis

The effect of the thermal anomaly of the underlying surface of the Tibetan Plateau in the previous winter and spring on the precipitation over the middle and lower reaches of the Yangtze River (MRYR) in the subsequent summer was investigated. Through data analysis, the influence of" strong signal" features of the three-dimensional thermal anomaly of the Plateau upon the precipitation anomaly over MRYR in the subsequent summer was revealed. This feature of the signal shows that from 0 cm to 320 cm under the surface of the ground, the soil temperature anomalies of the Tibetan Plateau manifest out of phase distribution in flood years and drought years over MRYR. In flood years over MRYR, there is a positive soil temperature anomaly in the region of the southern Tibetan Plateau (to the south of 30°N) and a negative anomaly in the region of the middle and northern Tibetan Plateau (to the north of 30°N), while in drought years the distribution of the soil temperature anomaly is opposite to the one in flood years. The maximum value of the soil temperature anomaly lies in the levels between 40 cm and 160 cm under the surface of the ground. Meanwhile, the data analysis also shows that the general circulation in the Northern Hemisphere may respond to the thermal anomaly of the Tibetan Plateau and form the propagation of a low frequency wave train with a seasonal time scale, and this wave train may affect the precipitation over MRYR in the subsequent summer.Analyses reveal that the thermal anomaly of the underlying surface of the Tibetan Plateau in the previous winter and spring is one of the key influencing factors for the subsequent summer precipitation over MRYR.