ENSO and convective activities in Southeast Asia and western Pacific

Abstract

The remarkable contrasts between El Niño and La Niña in the East/Southeast Asia region and the western Pacific region are reported. One is that the lightning flash rate in the East/Southeast Asia region shows a clear inverse correlation with the Southern Oscillation Index (SOI). The lightning activity increases during the El Niño period and decrease during the La Niña period in this area. The other is that the contrast of the areal distribution of the variation of the flash rate in the western Pacific region. During the El Niño period the moist air from the ocean is warmed over the land, and that makes strong updrafts in high-pressure systems over the oceanic area. As a result, well-developed cumulonimbus with frequent lightning activity is observed in the coastal area. During the La Niña period, low-pressure systems on the land cause the increase of rainfall frequency with less lightning activity. Copyright 2007 by the American Geophysical Union.