资源环境科技发展态势分析平台

The influences of different types of Pacific warming, often classified as the eastern Pacific (EP) and central Pacific (CP) El Nino events, on Madden-Julian oscillation (MJO) activity over the Indian Ocean were investigated. Accompanied by relatively unstable (stable) atmospheric stratification induced by enhanced (reduced) moisture and moist static energy (MSE) in the lower troposphere, strengthened (weakened) MJO convection was observed in the initiation and eastward-propagation stages during CP (EP) El Nino events. To examine the key processes resulting in the differences in low-level moistening and column MSE anomalies over the Indian Ocean associated with the two types of El Nino, the moisture and column MSE budget equations were diagnosed using the reanalysis dataset ERA-Interim. The results indicate that the enhanced horizontal advection in the CP El Nino years plays an important role in causing a larger moisture andMSE growth rate over theMJO initiation area during CP El Nino events than during EP ElNino events. The increases in horizontal moisture and MSE advection primarily result from advection by mean flow across the enhanced intraseasonal moisture andMSE gradient, as well as by intraseasonal circulation across the mean moisture and MSE gradient associated with the CP El Nino. In the eastward development stage, the enhanced preconditioning comes from positive moisture and MSE advection anomalies in the CP El Nino events. Meanwhile, the strengthened MJO-related convection over the central-eastern Indian Ocean is maintained by increased atmospheric radiative heating and surface latent heat flux during the CP El Nino compared to the EP El Nino events.