ENSO对MJO传播特征演变的影响

IMPACT OF ENSO ON MJO PROPAGATION BEHAVIORS

关键词:  MJO  季节内振荡  ENSO  垂直结构  水汽通量  传播

Key words:  Madden-Julian Oscillation  intraseasonal Oscillation  ENSO  vertical structure  moisture flux  propagation

摘要:

利用TRMM降水和ERA-Interim温度、比湿、环流场等再分析资料，探讨了在1998—2018年冬季年际尺度海温变化对MJO的强度、结构和传播特征的影响。主要结论如下：通过一种追踪MJO的方法在研究时间范围内共可挑选出50个MJO事件，其中有14个MJO事件发生在El Ni?o期间，25个发生在La Ni?a期间，11个发生在ENSO正常年。El Ni?o年MJO会传播至更远的中东太平洋附近，而La Ni?a年MJO事件趋于在西太平洋地区消亡，这主要与东太平洋地区持续的季节内尺度的经向水汽输送有关。此外，在印度洋和太平洋地区，El Ni?o年的MJO活动更强，而在海洋性大陆附近，La Ni?a年的MJO活动略强一些。ENSO对MJO强度的影响主要通过影响MJO对流中心东侧水汽的输送，水汽在异常东风气流的输送下穿过对流中心东边界进入对流中心，进而造成MJO活动强度的差异。

Abstract:

The present study identifies 50 MJO cases by using Madden Julian Oscillation (MJO) tracking method and TRMM precipitation, ERA-Interim temperature, specific moisture, and circulation data. The results show that 14 MJO events occurred in El Ni?o years, and 25 MJO events occurred in La Ni?a years. Moreover, most MJOs vanished in the western Pacific in La Ni?a years, while they could further propagate into the eastern Pacific and vanish there in El Ni?o years. The much shorter propagation range of MJO in La Ni?a years was due to the lack of moisture accumulation to the east of the MJO convective center when MJO propagated into the western Pacific. The MJO intensified in the Indian and Pacific Ocean in El Ni?o years due to the stronger moisture transport from the east to the MJO convective center. The larger amount of the moisture transport was attributed to the MJO zonal wind acting on the background moisture in El Ni?o years. In La Ni?a years, the MJO intensity was slightly stronger over the MC.