Analyzing the influences of two types of E1 Nifio on Tropical Cyclone Genesis with a modified genesis potential index

• Published in: 中国海洋湖沼学报：英文版 2017, Vol.35 (2), p.452-465
• Main Author: 杨宇星 杨磊 王法明
• Format: Article
• Language: English
• Subjects: 东太平洋; 修改; 分析数据; 厄尔尼诺; 大尺度环流; 热带气旋; 相对湿度; 阿拉伯海
• ISSN: 0254-4059; 1993-5005

To understand the impacts of large-scale circulation during the evolution of E1 Nifio cycle on tropical cyclones （TC） is important and useful for TC forecast. Based on best-track data from the Joint Typhoon Warning Center and reanalysis data from National Centers for Environmental Prediction for the period 1975- 2014, we investigated the influences of two types of E1 Nifio, the eastern Pacific E1 Nifio （EP-E1 Nifio） and central Pacific E1 Nifio （CP-E1 Nifio）, on global TC genesis. We also examined how various environmental factors contribute to these influences using a modified genesis potential index （MGPI）. The composites reproduced for two types of E1 Nifio, from their developing to decaying phases, were able to qualitatively replicate observed cyclogenesis in several basins except for the Arabian Sea. Certain factors of MGPI with more influence than others in various regions are identified. Over the western North Pacific, five variables were all important in the two E1Nifio types during developing summer （July-August-September） and fall （October- November-December）, and decaying spring （April-May-June） and summer. In the eastern Pacific, vertical shear and relative vorticity are the crucial factors for the two types of El Nifio during developing and decaying summers. In the Atlantic, vertical shear, potential intensity and relative humidity are important for the opposite variation of EP- and CP-EI Nifios during decaying summers. In the Southern Hemisphere, the five variables have varying contributions to TC genesis variation during peak season （January-February-March） for the two types of E1 Nifio. In the Bay of Bengal, relative vorticity, humidity and omega may be responsible for clearly reduced TC genesis during developing fall for the two types and slightly suppressed TC cyclogenesis during EP-E1 Nifio decaying spring. In the Arabian Sea, the EP-E1 Nifio generates a slightly positive anomaly of TC genesis during developing falls and decaying springs, but the MGPI failed to capture this variation.