热带气旋的温带变性过程对中纬度下游环流的影响

Impact of extratropical transition of tropical cyclone on the mid-latitude downstream flow

用WRF模式对变性台风(TC)马勒卡进行模拟,研究了在台风的变性过程(ET)的作用下中纬度下游环流特别是中纬度急流的发展,对台风的强度及其相对上游槽位置的敏感性。结果表明:TC与中纬度系统的相互作用会使得中纬度急流处的斜压不稳定性增大,急流增强。下游环流的发展对TC强度及TC与西风带上游槽的相对位置非常敏感。若TC增强,TC溢出流作用于中纬度急流,使之不稳定性增强,强度也增强,从而导致中纬度下游急流的强度、范围都增强,下游槽脊更显著。若台风减弱则反之。类似的,若TC靠近上游槽,其对中纬度急流的作用得到进一步加强和提前,急流的不稳定性增加,强度增强,下游的急流和槽脊也得到增强。若TC远离上游槽,则反之。

The Weather Research Forecasting （WRF） model is used to simulate the tropical cyclone （TC） ＂Malakas＂ in sensibility experiments such as ： ST （ TC enhanced） , NO （ TC weakened） , NW（ TC approached to the trough） and ES （TC left away from the trough）, and to investigate the development of downstream flow, especially the jet in mid-latitude. The results show that the interaction between TC and mid-latitude system would make the jet and its baroclinic instability enhance. The downstream flow is sen- sitive to the TC strength and TC position relative to the trough. If the TC strength enhances, the instability and intensity of TC outflow to the mid-latitude jet strengthen, resulting in the strengthening of both down- stream jet and ridge-trough. Vice versa. Similarly, if TC is closer to the upstream trough, its effect on the mid-latitude jet would further strengthen, making the jet more instable and stronger, and the downstream jet and ridge-trough enhance too. If TC is far away from upstrearm trough, the result is opposite.