Case analysis of a role of ENSO in regulating the generation of westerly wind bursts in the Western Equatorial Pacific
Case analysis of a role of ENSO in regulating the generation of westerly wind bursts in the Western Equatorial Pacific
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DOI：
10.1029/2002jc001498
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发表时间：
2003-04
影响因子：
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通讯作者：
Lisan Yu;R. Weller;W. Liu
中科院分区：
文献类型：
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作者：
Lisan Yu;R. Weller;W. Liu
通过对1996-2000年厄尔尼诺-南方涛动（ENSO）两个位相和1982年厄尔尼诺爆发的分析，推测低频ENSO可能对赤道西太平洋（WEP）的阵发性西风爆发（WWB）活动具有调节作用。结果表明，130°E ~ 160°E之间的赤道海平面气压梯度（SLP）是ENSO与WWB发生关系的关键参数。WEP是一个与中纬度大气瞬变强迫（冷涌）相关的热带气旋形成的预处理指数。赤道附近的气旋性环流有助于延长WWB事件。ENSO对南海暖水事件的影响主要是由于南海暖水事件的低层海平面气压中心的位置与暖水池的位置相关，并随ENSO位相的变化而发生东西向的迁移，从而决定了南海暖水事件的强度。通过太平洋海洋学方案的WEP，WWB的可变性与ENSO阶段相联系。研究发现，在1997年厄尔尼诺之前，当暖池较大并扩展到日界线附近时，CORP WEP被促进，而在1999/2000年拉尼娜之后，当暖池较小并向西移动时，CORP WEP被抑制。然而，只有在新几内亚东部产生的西风可能对ENSO具有潜在的重要性，因为印度尼西亚海域的岛屿对开尔文波的传播具有重要的阻碍作用。看来，活跃的WWB在1996年冬季产生的有利背景条件下，前厄尔尼诺状态，他们促进了1997年厄尔尼诺的发展，但可能不是一个足够的发病机制。本研究的案例分析所得出的假设的准确性还需要进一步的统计分析来检验。
This study speculates that the low-frequency ENSO might have a regulating effect on the activity of episodic westerly wind bursts (WWB) in the western equatorial Pacific (WEP) based upon the analysis of two contrasting El Nino-Southern Oscillation (ENSO) phases during the 1996-2000 period and the onset of the 1982 El Nino. It suggests that ⊇P WEP , the equatorial sea level pressure (SLP) gradient between 130°E and 160°E, could be a key parameter in relating ENSO to the WWB generation. ⊇P WEP is a preconditioning index for the tropical cyclone formation associated with midlatitude atmospheric transient forcing (cold surges). The cyclonic circulation near the equatorial latitudes contributes to prolonged WWB events. ⊇P WEP can be regulated by ENSO because the location of the low SLP center, which determines the strength of the ⊇P WEP , correlates with the location of the warm water pool, and has an east-west migration in response to the ENSO phases. Through ⊇P WEP , the variability of WWB was linked to the ENSO phases. The study finds that ⊇P WEP was promoted prior to the 1997 El Nino when the warm pool was large and extended to near the dateline, whereas it was suppressed during the follow on La Nina in 1999/2000 when the warm pool was small and displaced far westward. However, only westerly winds generated in the east of New Guinea could have potential importance to ENSO as the islands over the Indonesian Seas represent a significant blocking to the propagation of a Kelvin wave. It appears that the active WWB in the winter of 1996 were generated on a favorable background conditioned by pre-El Nino state; they facilitated the development of the 1997 El Nino but may not be a sufficient onset mechanism. Further statistical analysis is required to test the veracity of the hypothesis derived from the case analysis of this study.