热带大气高频温度异常对大气低频振荡影响的数值模拟研究

SIMULATION OF LFO′S RESPONSE TO TROPICAL HIGH FREQUENCY TEMPERATURE ANOMALY

用中国科学院大气物理研究所的 IAP 模式对发生在热带地区的高频温度异常进行了数值模拟。与控制试验结果对比,得知大气中的季节内振荡及双周振荡是大气变化的固有特性。当热带地区出现高频温度异常时,会影响大气中的各种物理量场,并以季节内振荡的响应最为明显。其主要表现是使原有的中高纬度季节内振荡作用减弱,而高频振荡部分加强。对异常响应的作用在低纬地区表现为:中上层以相当快的速度向东西两个方向传播,尤其以向东传播更为显著。第一候就在距扰源2万公里的低纬处形成了遥相关。从传播的速度、扰动的波长等方面看,与罗斯贝-重力混合波的作用一致。对这种异常响应的作用,除高纬度地区是自东向西传播外,中低纬地区主要是向东传播。其响应作用的南北向传播主要在某些特定地区比较明显,表现为由中高纬向低纬传送。

Numerical study is carried out of tropical high frequency temperature anomaly in the context of the IAP model developed by the Institute of Atmospheric Physics,Beijing.Compari- son of the findings to those from a control experiment shows that the intraseasonal and biweekly oscillations are properties inherent in the atmosphere;high-frequency anomaly in tropical temper- ature will give rise to change in physical quantity fields,particularly in the context of intraseason- al oscillation,with primary alterations in weakening the original intraseasonal and intensifying the high-frequency portion of the oscillation at extratropics;the response is displayed tropically by the travel at great pace to the east,predominantly,and west,to less degree,in the mid and up- per level atmosphere so that a teleconnection pattern is generated at low latitudes between the dis- turbance source and a place 20000 km away.It is noted that the perturbation resembles a type of mixed Rossby-gravity waves as regards velocity. The response takes the form of east-to-west propagation in high latitudes and dominantly eastward shift over mid-low latitudes,with meridional,chiefly equatorward,migration in some particular areas.