西伯利亚风暴轴的气候特征及其可能维持机制

基于1959—2014年NCEP/NCAR的逐日再分析资料,首先研究了西伯利亚风暴轴各季节的气候平均特征,然后以冬季为例,利用能量诊断方程,从能量学的角度对其的可能维持机制进行了探讨,并在上述分析过程中与北半球两大洋风暴轴的特征进行了对比。结果表明:(1)西伯利亚风暴轴一年四季都独立存在,虽强度要比两大洋风暴轴的强度弱很多且位置偏北,但可以定义为一个弱风暴轴。(2)比较来看,西伯利亚风暴轴强度的季节变化与北太平洋风暴轴的季节变化类似。与两大洋风暴轴位于急流东北侧不同,冬季西伯利亚风暴轴位于东亚温带急流的西侧。(3)进一步的能量分析结果表明,与两大洋风暴轴一样,斜压不稳定的能量转换(Ke4)也是西伯利亚风暴轴区域天气尺度扰动动能的主要来源;而扰动非地转位势通量散度项(Ke3)和时间平均气流对扰动动能的平流输送项(Ke1)也是风暴轴下游发展所需的扰动动能来源之一。

The climatic characteristics of Siberian storm track and its possible maintenance mechanism

Based on the daily NCEP/NCAR reanalysis data during 1959-2014, the climatic mean characteristic of Siberian storm track was firstly investigated. And then, the energy diagnostic equation was used to discuss its possible maintenance mechanism in winter and compared with Siberian storm track with the North Pacific Storm Track (NPST) and Northern Atlantic Storm Track (NAST). Results show that:(1) Siberian storm track exists independently in four seasons. Although its intensity is the weakest and its position is to the north compared with the NPST and NAST, it still can be defined as a weak storm track. (2) The seasonal variation of Siberian storm track intensity is similar to that of the NPST. Unlike the northeastern location of the jet of two oceanic storm tracks, the Siberian storm track is located on the west side of the East Asian Polar-front Jet. (3) The further energy analysis results show that the baroclinic energy conversion (K_e4) is the main energy source of the Siberian storm track. The advective transport term of time-averaged airflow to eddy kinetic energy (K_e1) and eddy ageostrophic geopotential flux (K_e3) also play an important roles in the maintenance of the storm track in its eastern part.