Seasonal variation of barrier layer in the southeastern tropical Indian Ocean

Abstract Eastern China has a large population with rapid development of the economy, where is the important crop producing region. In this region, the spatial and temporal distribution of autumn rainfall in Eastern China is uneven, which has important societal impact. Using the NCEP–NCAR reanalysis and other observational datasets, it is found that the spatial distribution of the first EOF mode of autumn rainfall anomalies in eastern China is consistent across the region, with significant interannual variabilities. Pronounced interdecadal variations are presented in the relationship between autumn rainfall anomalies in eastern China and sea-surface temperature anomalies (SSTA) over the southeastern tropical Indian Ocean (SETIO). The interdecadal changes have been analyzed by considering two epochs: one during 1979-2004 and the other during 2005-2019. It shows weak and insignificant correlations between the autumn rainfall anomalies in eastern China and SSTA over SETIO during the first epoch. On the other hand, they are remarkable and positively correlated with each other during the second epoch. The inter-decadal changes of the above relationship are related to the warming of SST over SETIO during the second epoch. It causes stronger low-level convergence and ascending motion over SETIO, with the co-occurrence of enhanced western Pacific subtropical high and anomalous abundant moisture over eastern China carried by a low-level southerly anomaly originating from the South China Sea. Simultaneously, the local Hadley circulation over eastern China becomes weak, corresponding to the anomalous ascending motion. The collaboration of anomalous water vapour transport and ascending motion strengthens the connection between the SETIO SSTA and the autumn precipitation anomalies in eastern China, and vice versa. In the boreal autumn of 2019, entire eastern China suffered extreme drought. It suggests that this drought event in eastern China is strongly affected by the negative SSTA over SETIO, which is consistent with the statistical results.

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Numerical study of the effects of ocean color on the sea surface temperature in the southeast tropical Indian Ocean: the role of the barrier layer

Environmental Research Letters ◽

10.1088/1748-9326/7/2/024010 ◽

2012 ◽

Vol 7 (2) ◽

pp. 024010 ◽

Cited By ~ 5

Author(s):

Hailong Liu ◽

Jinfeng Ma ◽

Pengfei Lin ◽

Haigang Zhan

Keyword(s):

Indian Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Barrier Layer ◽

Numerical Study ◽

Ocean Color ◽

Tropical Indian Ocean ◽

Sea Surface

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Interannual Climate Variability over the Tropical Pacific Ocean Induced by the Indian Ocean Dipole through the Indonesian Throughflow

Journal of Climate ◽

10.1175/jcli-d-12-00117.1 ◽

2013 ◽

Vol 26 (9) ◽

pp. 2845-2861 ◽

Cited By ~ 39

Author(s):

Dongliang Yuan ◽

Hui Zhou ◽

Xia Zhao

Keyword(s):

Pacific Ocean ◽

Indian Ocean ◽

Tropical Indian Ocean ◽

Sea Surface Height ◽

Equatorial Pacific ◽

Sea Surface ◽

Indonesian Throughflow ◽

Cold Tongue ◽

The Indian Ocean ◽

Southeastern Tropical Indian Ocean

Abstract The authors’ previous dynamical study has suggested a link between the Indian and Pacific Ocean interannual climate variations through the transport variations of the Indonesian Throughflow. In this study, the consistency of this oceanic channel link with observations is investigated using correlation analyses of observed ocean temperature, sea surface height, and surface wind data. The analyses show significant lag correlations between the sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean in fall and those in the eastern Pacific cold tongue in the following summer through fall seasons, suggesting potential predictability of ENSO events beyond the period of 1 yr. The dynamics of this teleconnection seem not through the atmospheric bridge, because the wind anomalies in the far western equatorial Pacific in fall have insignificant correlations with the cold tongue anomalies at time lags beyond one season. Correlation analyses between the sea surface height anomalies (SSHA) in the southeastern tropical Indian Ocean and those over the Indo-Pacific basin suggest eastward propagation of the upwelling anomalies from the Indian Ocean into the equatorial Pacific Ocean through the Indonesian Seas. Correlations in the subsurface temperature in the equatorial vertical section of the Pacific Ocean confirm the propagation. In spite of the limitation of the short time series of observations available, the study seems to suggest that the ocean channel connection between the two basins is important for the evolution and predictability of ENSO.

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Seasonal Characteristics of Circulation in the Southeastern Tropical Indian Ocean*

Journal of Physical Oceanography ◽

10.1175/jpo-2682.1 ◽

2005 ◽

Vol 35 (2) ◽

pp. 255-267 ◽

Cited By ~ 41

Author(s):

Tangdong Qu ◽

Gary Meyers

Keyword(s):

Indian Ocean ◽

Annual Variation ◽

Maximum Amplitude ◽

Tropical Indian Ocean ◽

Surface Flow ◽

Sea Surface ◽

The South ◽

Near Surface ◽

Seasonal Characteristics ◽

Southeastern Tropical Indian Ocean

Abstract The circulation in the southeastern tropical Indian Ocean is studied using historical temperature and salinity data. A southward shift of the subtropical gyre at increasing depth dominates the structure of the annual mean circulation. Near the southern Indonesian coast the westward South Equatorial Current (SEC) is at the sea surface and strongest near 10°–11°S, reflecting strong influence of the Indonesian Throughflow (ITF). In latitudes 13°–25°S the SEC is a subsurface flow and its velocity core deepens toward the south, falling below 500 m at 25°S. The eastern gyral current (EGC) is a surface flow overlying the SEC, associated with the meridional gradients of near-surface temperature and salinity. The ITF supplies water to the SEC mainly in the upper 400 m, and below that depth the flow is reversed along the coast of Sumatra and Java. Monsoon winds strongly force the annual variation in circulation. Dynamic height at the sea surface has a maximum amplitude at 10°–13°S, and the maximum at deeper levels is located farther south. Annual variation is also strong in the coastal waveguides, but is mainly confined to the near-surface layer. Although the South Java Current at the sea surface is not well resolved in the present dataset, semiannual variation is markedly evident at depth and tends to extend much deeper than the annual variation along the coast of Sumatra and Java.

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Nutrient enrichment induced by tropical cyclone Seroja in the southeastern tropical Indian Ocean

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/925/1/012021 ◽

2021 ◽

Vol 925 (1) ◽

pp. 012021

Author(s):

D W Purnaningtyas ◽

F Khadami ◽

Avrionesti

Keyword(s):

Tropical Cyclone ◽

Indian Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Nutrient Enrichment ◽

Tropical Indian Ocean ◽

Sea Surface ◽

Nutrient Concentrations ◽

Biochemical Alterations ◽

Southeastern Tropical Indian Ocean

Abstract Tropical cyclone (TC) passage triggers a complex response from the adjacent ocean, including vertical mixing, leading to biochemical alterations and affecting the surrounding ecosystem’s dynamics. In previous studies, increased nutrient concentrations and primary production were observed along the cyclone track after the storm. TC Seroja was awakened near the equator in the southeastern tropical Indian Ocean, making it interesting to investigate how the ambient ecosystem responds. Hence, we analyzed the sea surface temperature and nutrient changes during the Seroja event using multi-satellite remote sensing and numerical model data in the south of Indonesia and East Timor along the Seroja track between April 2 and 10, 2021. Immediately after the TC Seroja passed, the sea surface temperature cooled to 3 °C around the TC lane. At the same time, the spatial distribution patterns showed the upsurge of some nutrients in response to the passage of TC Seroja; the surface nitrate swells up to 1.5 mmol/m3, while phosphate increased up to 0.2 mmol/m3, and the dissolved silicate concentration enhanced up to 1.0 mmol/m3. The responses recover within 2-7 days. These results indicate that tropical cyclones contribute to nutrient enrichment in oligotrophic areas outside of their usual annual upwelling time, thereby further supporting ecosystem sustainability.

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Structure and Seasonal Variation of the Indian Ocean Tropical Gyre Based on Surface Drifters

10.5194/egusphere-egu21-6871 ◽

2021 ◽

Author(s):

Wei Wu ◽

Yan Du ◽

Yu-Kun Qian ◽

Xuhua Cheng ◽

Tianyu Wang ◽

...

Keyword(s):

Seasonal Variation ◽

Indian Ocean ◽

Water Mass ◽

Southern Oscillation ◽

Tropical Indian Ocean ◽

Western Boundary ◽

Boundary Current ◽

Boreal Spring ◽

The Indian Ocean ◽

Surface Drifters

<p>Using the Gauss&#8211;Markov decomposition method, this study investigates the mean structure and seasonal variation of the tropical gyre in the Indian Ocean based on the observations of surface drifters. In the climatological mean, the clockwise tropical gyre consists of the equatorial Wyrtki Jets (WJs), the South Equatorial Current (SEC), and the eastern and western boundary currents. This gyre system redistributes the water mass over the entire tropical Indian Ocean basin. Its variations are associated with the monsoon transitions, featuring a typical clockwise pattern in the boreal spring and fall seasons. The relative importance of the geostrophic and Ekman components of the surface currents as well as the role of eddy activity were further examined. It was found that the geostrophic component dominates the overall features of the tropical gyre, including the SEC meandering, the broad eastern boundary current, and the axes of the WJs in boreal spring and fall, whereas the Ekman component strengthens the intensity of the WJs and SEC. Eddies are active over the southeastern tropical Indian Ocean and transport a warm and fresh water mass westward, with direct impact on the southern branch of the tropical gyre. In particular, the trajectories of drifters reveal that during strong Indian Ocean Dipole or El Ni&#241;o-Southern Oscillation events, long-lived eddies were able to reach the southwestern Indian Ocean with a moving speed close to that of the first baroclinic Rossby waves.</p>

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