Impacts of detoured madden-julian oscillations on the south pacific convergence zone

Abstract

Madden-Julian oscillations (MJOs) are a major component of tropical intraseasonal variabilities. There are two paths forMJOs across theMaritime Continent; one is a detoured route into the SouthernHemisphere and the other one is around the equator across the Maritime Continent. Here, it is shown that the detoured and nondetoured MJOs have significantly different impacts on the South Pacific convergence zone (SPCZ). The detoured MJOs trigger strong cross-equatorial meridional winds from the Northern Hemisphere into the Southern Hemisphere. The associated meridional moisture and energy transports due to the background states carried by the intraseasonal meridional winds are favorable for reinforcing the SPCZ. In contrast, the influences of nondetouredMJOs on either hemisphere or the meridional transports across the equator are much weaker. The detouredMJOs can extend their impacts to the surrounding regions by shedding Rossby waves.Due to different background vorticity during detouredMJOs in boreal winter, more ray paths of Rossby waves traverse theMaritime Continent connecting the southern Pacific Ocean and the eastern Indian Ocean, but far fewer Rossby wave paths traverse Australia. Further studies on such processes are expected to contribute to a better understanding of extreme climate and natural disasters on the rim of the southern Pacific and Indian Oceans.