2010/2011年中部型La Nia事件形成机理及其垂直环流异常

The Formation Mechanism of the Central Pacific Pattern La Nia Event in 2010/2011 and Its Anomalous Vertical Circulation

应用TAO(Tropical Atmosphere Ocean project)热带太平洋实测海温和风场资料,分析研究了2010/2011年La Nia事件的变化特征,讨论了此次过程中赤道太平洋次表层异常海温的变化特征及其传播过程,以及上层海温场的异常变化机理。结果表明,2010/2011年的La Nia事件与传统事件不同,是一次明显的中部型La Nia事件(简称CPP La Nia),其爆发过程主要存在两个不同机制的响应过程:一是西太平洋暖池(WPWP)区域次表层异常冷海温通过赤道潜流的作用沿温跃层东传,导致赤道东太平洋上层海洋温度场出现异常降温:二是赤道中东太平洋出现强的距平东风,通过上升流作用,导致冷海温上传影响中太平洋上层异常海温场。前者是导致La Nia事件的必要条件,后者则是形成此次中部型La Nia事件的关键过程。由分析结果还表明,日界线以东赤道太平洋纬向风变化对中西太平洋上层海温场变化有重要影响,是导致此次中部型事件爆发的重要机制。文章进一步分析了此次中部型La Nia事件过程中热带垂直环流的变化,结果表明经向和纬向大气环流都表现出明显的异常。

The variability of La Nifia event in 2010/2011 was analyzed using the temperature and wind data from Tropical Atmosphere Ocean （TAO） project dataset,and the variation and propagation of the anoma- lous subsurface ocean temperature in equatorial Pacific and the mechanism of anomalous variations of the upper ocean temperature field were discussed. The results indicate that the La Ni a event in 2010/2011, which differs canonical La Ni a events, is an obvious central pacific pattern La Ni a event （CPP La Ni a）. Its outburst includes mainly two different response processes, one is that the subsurface ocean temperature anomalies in the western Pacific warm pool （WPWP） propagate eastward along the thermocline through the action of equatorial undercurrent and eventually make the upper eastern equatorial Pacific Ocean cooled; and another is that strong easterly wind anomaly in the central and＇eastern equatorial Pacific causes the temperature of cold water to propagate from the subsurface to the surface through upwelling and even- tually makes the surface water in the central pacific cooled. The former is a necessary condition leading to the La Ni a event, while the latter is the key process forming this CPP La Ni a event. The results also indi- cate that the variations of the zonal wind in the tropical pacific east of the dateline influence significantly on the anomalous ocean temperature field in the upper central western Pacific ocean, which is one of the most important mechanisms causing the outburst of the CPP La Ni a event in the 2010/2011. The variations of the vertical circulation occurring in the tropical zone during the CPP La Ni a event are also analyzed, indi- cating that both the longitudinal and the latitudinal atmospheric circulations show significant anomalies.