Tomoki Tozuka

Abstract The decadal variation in the tropical Indian Ocean is investigated using outputs from a 200-yr integration of the Scale Interaction Experiment-Frontier Research Center for Global Change (SINTEX-F1) ocean–atmosphere coupled model. The first EOF mode of the decadal bandpass- (9–35 yr) filtered sea surface temperature anomaly (SSTA) represents a basinwide mode and is closely related with the Pacific ENSO-like decadal variability. The second EOF mode shows a clear east–west SSTA dipole patt

Abstract. Over the past decade, our understanding of the Indian Ocean has advanced through concerted efforts toward measuring the ocean circulation and air–sea exchanges, detecting changes in water masses, and linking physical processes to ecologically important variables. New circulation pathways and mechanisms have been discovered that control atmospheric and oceanic mean state and variability. This review brings together new understanding of the ocean–atmosphere system in the Indian Ocean sin

Using OGCM experiments with and without the South China Sea throughflow, it is shown that this throughflow plays an important role in generating the subsurface maxima in the meridional velocity of the Makassar Strait throughflow. The maximum in the southward flow is located at subsurface around 110 m in the control run, whereas that exists near the surface without the South China Sea throughflow. This results in 0.18 PW difference in the southward heat transport by the Makassar Strait throughflo

Using a high-resolution OGCM result, multiscale variations of the Mindanao Dome (MD) are discussed. The MD is generated by local Ekman upwelling as the positive curl of the Asian winter monsoon increases over the western tropical Pacific, as discussed in the literature. It is shown, however, that the MD decays owing to the Pacific basinwide annual cycle; the warm anomaly that propagates from the eastern tropical Pacific plays an important role in the attenuation of the MD. Also, the negative win

Interannual variations of the Seychelles Dome (SD) in the southwestern Indian Ocean are investigated using outputs from an ocean general circulation model. The high variability is locked seasonally to boreal winter. The SD becomes anomalously weak (strong) owing to anomalous local Ekman downwelling (upwelling) and arrival of downwelling (upwelling) Rossby waves excited in the southeastern Indian Ocean. In contrast to past studies, the anomalous local Ekman pumping cannot be neglected in discussi

Abstract Using various observational data, the seasonal cycle of the tropical Pacific is investigated, suggesting the existence of an “annual El Niño–Southern Oscillation (ENSO).” A positive sea surface temperature anomaly (SSTA) appearing off Peru in boreal winter triggers a series of air–sea interactions that consist of westward propagations of positive SSTA, westerly wind anomalies, and negative outgoing longwave radiation anomalies. At the same time, the westerly wind anomaly generates cold

Abstract The Walker circulation is the key component of the atmospheric zonal circulation in the tropics. In this study, it is shown that anomalous Walker circulations associated with two types of the Indian Ocean Dipole (IOD) are remarkably different. During a positive canonical IOD with negative (positive) sea surface temperature (SST) anomalies in the eastern (central to western) tropical Indian Ocean, a single‐cell anomalous Walker circulation forms over the Indian Ocean. On the other hand,

Causes of the coupled model bias in simulating the zonal sea surface temperature (SST) gradient in the equatorial Atlantic are examined in three versions of the same coupled general circulation model (CGCM) differing only in the cumulus convection scheme. One version of the CGCM successfully simulates the mean zonal SST gradient of the equatorial Atlantic, in contrast to the failure of the Coupled Model Intercomparison Project phase 3 models. The present analysis shows that key factors to be suc

Air-sea interaction processes that modify the sea surface temperature (SST) front in the Agulhas Return Current region (between 40°E and 55°E) during austral summer and winter are examined using observational data and output from a high-resolution ocean general circulation model. While the air-sea heat flux frontal variations tend to relax the SST front, the frontolysis is amplified (damped) in summer (winter) when frontal variations in the mixed layer depth (MLD) are incorporated. The stronger