南海-西北太平洋季风槽中热带气旋群发的研究Ⅱ.影响机制研究
Research on the cluster of tropical cyclogenesis in the South China Sea-western north Pacific monsoon trough Ⅱ. Mechanism of the influence
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摘要: 应用1979-2005年西北太平洋热带气旋(TC)资料和OLR,NCEP/DOE AMIP-Ⅱ再分析逐日资料,探讨南海-西北太平洋季风槽中TC(简称MTTC)群发的可能机理,得到以下几点结论:(1)5~10月季风槽强度及形态与索马里越赤道气流的强弱、副高的位置以及南半球澳洲冬季风的强弱密切相关,不同区域季风槽强度增强都可能导致MTTC群发。(2)MTTC群发与季风槽强度的低频振荡密切相关,当季风槽强度30~60 d振荡处于活跃期,准双周10~20 d的振荡也处于活跃期时,有利于MTTC的群发。(3)副高的位置、索马里越赤道气流以及西太平洋越赤道气流的低频振荡的位相配置将影响季风槽强度和形态,进而影响MTTC群发。副高东退或位置偏北,索马里越赤道气流或西太平洋越赤道气流增强或同时增强,季风槽偏北或东伸,皆有利于MTTC群发;副高偏西偏南,索马里越赤道气流增强或西太平洋越赤道气流增强,季风槽偏南,该类型MTTC群发比例较低,群发次数偏少。(4)典型个例分析表明,由于季风槽强度和形态的差异造成MTTC主要生成区对流条件以及水汽条件的差异,致使MTTC群发的年际差异。
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关键词:
- 南海-西北太平洋季风槽 /
- 热带气旋 /
- 群发 /
- 影响机制
Abstract: By using the western north Pacific tropical cyclone(TC)data, OLR data and the NCEP/DOE AMIP-Ⅱ reanalysis daily data during 1979-2005, the possible mechanism of the cluster of TCs in the South China Sea (SCS)-western north Pacific monsoon trough (CTC) are discussed, the main results are as follows: (1)During May-October, the intensity and pattern of monsoon trough are closely related to the strength of Somalia’s cross-equatorial flow, the location of western north Pacific subtropical high (WNPSH) and the intensity of the Southern Hemisphere Australian winter monsoon. Enhanced intensity of monsoon trough in different regions may lead to CTC. (2) CTC and the low-frequency oscillations of monsoon trough are closely connected.. the CTC often occurs when the monsoon trough is in the active phase both of 10~20 and 30~60 d oscillations . (3) CTC is affected by intensity and pattern of monsoon trough which are related to the location of WNPSH, the intra-seasonal oscillation phases of cross-equatorial flows over the Somalia and western Pacific. It supplies favorable conditions to CTC when WNPSH retreats to eastward or is in the north of mean and the cross-equatorial flows enhance either over Somalia or the western Pacific, as well as enhance in both of them. When WNPSH is west and south to the normal, the cross-equatorial flows enhance over Somalia area or the western Pacific, the monsoon trough is located southward leading to less CTC. (4) Typical cases analysis shows that CTC exhibits inter-annual variation due to the different convection and moisture conditions in the main TC generating areas which are caused by the different intensity and pattern of monsoon trough. -
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