雙眼牆結構多出現於強度較高的颱風，相較於一般颱風結構，雙眼牆結構是由眼牆外再發展出一環狀強對流帶，產生第二眼牆，近颱風中心的眼牆為內眼牆，較遠的第二眼牆則為外眼牆，外眼牆與內眼牆之間有一對流極小的區域moat，且眼牆彼此同心，故又稱同心眼牆(Concentric Eyewall)。Willoughby et al. (1982) 提出眼牆置換週期(Eyewall Replacement Cycle)論述，多數雙眼牆結構形成後，外眼牆逐漸增強，位置逐漸內縮，內眼牆則是逐漸減弱並隨著外眼牆內縮而消散。 為了研究西北太平洋雙眼牆颱風眼牆置換過程與颱風整體平均降雨強度之關係，本文利用蕭(2013)的方法以及GSMaP(Global Satellite Mapping of Precipitation)高解析度資料取得內外眼牆強度與颱風整體平均降雨強度之時序變化發現雙眼牆颱風整體平均降雨強度不一定會同時受到內外眼牆強度改變而有很大的影響，依照眼牆對於颱風整體平均降雨強度的影響程度來看可將雙眼牆颱風個案分成三個類別: 內眼牆、外眼牆、內外眼牆主導降水強度。 內眼牆主導降水強度個案的颱風整體平均降雨強度與內眼牆強度變化有相似的趨勢，儘管外眼牆強度增強，總雨量仍沒有提升的現象發生；外眼牆主導降水強度個案的降雨強度則是與外眼牆強度變化有相似的趨勢，當內眼牆逐漸減弱消散時，颱風整體平均降雨強度仍然有維持或是有上升的趨勢；內外眼牆主導降水強度個案，其颱風整體平均降雨強度會同時受到內外眼牆變化影響。 如果可以掌握雙眼牆颱風類別即可進一步推估颱風整體平均降雨強度趨勢，而造成不同眼牆主導颱風整體平均降雨強度的原因則仍需要進一步的分析。 ;Strong typhoons usually have double eyewall structure. Comparing with normal typhoons, double eyewall typhoons have an inner eyewall and outer eyewall separated by the moat which is convective minimum region. Because inner eyewall and outer eyewall both surround the center of typhoon, this structure also called Concentric Eyewall (CE). Willoughby et al. (1982) indicated the eyewall replacement cycle dynamics. Radius outer eyewall contract and increase intensity. Conversely, radius inner eyewall decreased intensity. Finally, the inner eyewall dissipate and replaced by the outer eyewall. For studying the relationship of western North Pacific typhoons′ eyewall replacement cycle and total average rainfall rate, this work adopt the method of Hsiao (2013) and GSMaP (Global Satellite Mapping of Precipitation) data which has high spatial and temporal resolution. The result appear that not both inner eyewall and outer eyewall affect CE typhoons′ total average rainfall rate strongly. Depending on influence of inner eyewall and outer eyewall, the three types of CE typhoons has been set: inner eyewall domination, outer eyewall domination and both eyewall domination. The cases of inner eyewall domination which typhoons′ total average rainfall rate has similar tendency change with inner eyewall′s rainfall rate intensity. Despite the rainfall rate intensity of outer eyewall enhanced, typhoons′ total average rainfall rate doesn′t be enhanced; the cases of outer eyewall domination which typhoons′ total average rainfall rate has similar tendency change with outer eyewall′s rainfall rate intensity. When the rainfall rate intensity of inner eyewall dissipate, typhoons′ total average rainfall rate still maintain or even enhance intensity; the both eyewall of inner eyewall domination which typhoons′ total average rainfall rate will be affected by both inner eyewall and outer eyewall obviously. If the type of CE typhoons can be known previously, we can forecast tendency change of typhoons′ total average rainfall rate. The reason for causing different eyewall dominate typhoons′ total average rainfall rate is still needed to be investigated.
