Global Impact of ENSO events by TRMM observations

摘要

El Ni(n)o Southern Oscillation (ENSO)is a disruption of the ocean-atmosphere systems in the Tropical Pacific having impact for atmospheric phenomena globally.The lightning flash rate observed by TRMM/LIS in the East/South-East Asia region shows clear inverse correlation to Southern Oscillation Index (SOI)with the correlation factor of -0.73.Briefly,the lightning activities increase during El Ni(n)o period,and decrease during La Ni(n)a period in the region.It is noticeable that the sea level pressure is higher during El Ni(n)o period than that of average value,in the oceanic area especially in the north-east of Indonesia and the north-west of Australia.This high-pressure systems decrease up-drafts,and the rainfall frequency is diminished in the same region.In the regions having the remarkable anomalies of sea level pressure,however,the anomalies of wind vectors from the ocean to the land are noticeable.The contrast of the sea level pressure between on the sea and on the land highly related to the sea breeze obviously.It is considered that the damp air from the ocean is warmed up on the land,and that makes strong up drafts.As a result,well-developed cumulonimbus with energetic lightning activities is observed in the coastal area.During La Ni(n)a period,on the other hand,lower sea level pressures make many low-pressure systems causing increase of rainfall frequency.Though the results in this study are preliminary and further investigation and more evidences are needed,we found the implications of the change in convective activities due to El Ni(n)o and La Ni(n)a events on the lightning activity and their possible correlations with some parameters for storms.In this paper rainfall frequency,rainfall intensity,altitude of PR radar echo top,wind vector,sea level pressure and so forth are discussed as well as the lightning flash rate around the globe.