The Bay of Bengal (BoB) summer monsoon is often triggered by northward propagating intraseasonal oscillations (ISOs) in the eastern Indian Ocean. The timing of summer monsoon onset, with a mean date of 1 May and standard deviation of 13 days, is substantially advanced (delayed) following a cold (warm) ENSO event. In this study, the significant ENSO‐onset anomaly relationship is understood by investigating the ENSO modulations on the pivotal monsoon trigger. In the decaying spring of a cold (warm) ENSO event, pronounced easterly (westerly) vertical wind shear anomalies are induced in the northern Indian Ocean due to the enhanced (suppressed) convection anomalies in the northwestern Pacific Ocean. The above interannual vertical shear difference dominantly (more than 60%) contributes to a distinct ISO intensity contrast in the northern BoB. Consequently, the strengthened (weakened) ISOs associated with cold (warm) ENSO events lead to advanced (delayed) onsets of BoB summer monsoon.

While the effects of the Southern Annular Mode (SAM), a dominant climate variability mode in the Southern Ocean, on ocean acidification have been examined using models, no consensus has been reached. Using observational data from south of Tasmania, we show that during a period with positive SAM trends, surface water pH and aragonite saturation state at 60°–55° S (Antarctic Zone) decrease in austral summer at rates faster than those predicted from atmospheric CO₂ increase alone, whereas an opposite pattern is observed at 50°–45° S (Subantarctic Zone). Together with other processes, the enhanced acidification at 60°–55° S may be attributed to increased westerly winds that bring in more “acidified” waters from the higher latitudes via enhanced meridional Ekman transport and from the subsurface via increased vertical mixing. Our observations support climatic modulation of ocean acidification superimposed on the effect of increasing atmospheric CO₂.

A significant sea surface temperature (SST) drop was clearly identified to be confined exactly over the Yellow Sea Cold Water Mass (YSCWM) from satellite‐derived SSTs during Typhoon Muifa's passage over the Yellow Sea (YS) in early August 2011. With a simple one‐dimensional mixed‐layer model (Price‐Weller‐Pinkel [PWP]), the mixed‐layer heat budget diagnosis concluded that the entrainment term, rather than the surface heat flux term that usually dominates over the open ocean, was the dominant process for the significant SST cooling over the YSCWM. The PWP‐based experiments were conducted to set up one lookup table including the SST drop, wind speed, and subsurface temperature gradient, from which the YSCWM's intensity (represented by the subsurface temperature gradient) can be easily found with the satellite wind and SST measurements during the typhoon passage over the YS. This YSCWM‐anchored significant SST drop provides a promising possibility to detect the YSCWM intensity and extent, which have generally been poorly sampled to date.

This study investigates the northward-propagating quasi-biweekly oscillation (QBWO) in the western North Pacific by examining the composite meridional structures. Using newly released reanalysis and remote sensing data, the northward propagation is understood in terms of the meridional contrasts in the planetary boundary layer (PBL) moisture and the column-integrated moist static energy (MSE). The meridional contrast in the PBL moisture, with larger values north of the convection center, is predominantly attributed to the moisture convergence associated with barotropic vorticity anomalies. A secondary contribution comes from the meridional moisture advection, for which advections by mean and perturbation winds are almost equally important. The meridional contrast in the MSE tendency, due to the recharge in the front of convection and discharge in the rear of convection, is jointly contributed by the meridional and vertical MSE advections. The meridional MSE advection mainly depends on the moisture processes particularly in the PBL, and the vertical MSE advection largely results from the advection of the mean MSE by vertical velocity anomalies, wherein the upper-troposphere ascending motion related to the stratiform heating in the rear of the convection plays the major role. In addition, partial feedback from sea surface temperature (SST) anomalies is evaluated on the basis of MSE budget analysis. SST anomalies tend to enhance the surface turbulent heat fluxes ahead of the convention center and suppress them behind the convention center, thus positively contributing approximately 20% of the meridional contrast in the MSE tendency.

The Maritime Continent (MC) often exerts barrier effect on the eastward propagation of the Madden‐Julian Oscillation (MJO), and the strongest (weakest) effect occurs in spring (winter). After passing over the MC, the MJO slightly weakens by approximately 10% in winter and it sharply decays by more than 50% in spring. The physics for this spring barrier are understood from the perspective of the frictionally coupled Kelvin‐Rossby wave theory. In spring, the abrupt reduction in the boundary layer moisture convergence that occurs at the MC causes the decoupling of the Kelvin‐Rossby wave packet associated with the MJO: Kelvin waves emit from the major convection, while Rossby wave component rapidly decays in the Indian Ocean. An intermediate atmospheric model involving both the fundamental dynamics of the frictionally coupled Kelvin‐Rossby wave theory and the mean states confirms that the spring barrier is determined primarily by the mean surface moisture, particularly by its zonal distribution.

Internal waves (IWs) mitigate thermal stress and provide refugia for corals against increasingly frequent mass bleaching. However, climate events may bring uncertainty regarding the resistance of such refugia. Here, using in situ observation data in the Andaman Sea (AS), we conduct a case study in which a monsoon anomaly associated with an El Niño event threatens IW coral refugia. IW cooling in the AS coral reefs is modulated by the thermocline depth variation, which is driven, to a significant extent, by Kelvin wave signals from the equator. In the pre-monsoon period, distinct variations in IW cooling and surface heating form a time window of quickly-growing cumulative heat exposure. The El Niño induces a typical two-week delay of summer monsoon onset, which prolongs the duration of thermal stress growth and brings severe bleaching risk to corals. As global warming increases the frequency of extreme El Niño events, IW coral refugia will face great challenges in the future.