Indian Ocean warming during peak El Niño cools surrounding land masses

ABSTRACTPrevious studies linked the increase of the middle and low reaches of the Yangtze River (MLRYR) rainfall to tropical Indian Ocean warming during extreme El Niños’ (e.g., 1982/83 and 1997/98 extreme El Niños) decaying summer. This study finds the linkage to be different for the recent 2015/16 extreme El Niño’s decaying summer, during which the above-normal rainfalls over MLRYR and northern China are respectively linked to southeastern Indian Ocean warming and western tropical Indian Ocean cooling in sea surface temperatures (SSTs). The southeastern Indian Ocean warming helps to maintain the El Niño–induced anomalous lower-level anticyclone over the western North Pacific Ocean and southern China, which enhances moisture transport to increase rainfall over MLRYR. The western tropical Indian Ocean cooling first enhances the rainfall over central-northern India through a regional atmospheric circulation, the latent heating of which further excites a midlatitude Asian teleconnection pattern (part of circumglobal teleconnection) that results in an above-normal rainfall over northern China. The western tropical Indian Ocean cooling during the 2015/16 extreme El Niño is contributed by the increased upward latent heat flux anomalies associated with enhanced surface wind speeds, opposite to the earlier two extreme El Niños.

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Remote forcing of Indian Ocean warming on Northwest Pacific during El Niño decaying years: a FOAM model approach

Chinese Journal of Oceanology and Limnology ◽

10.1007/s00343-013-3075-1 ◽

2013 ◽

Vol 31 (6) ◽

pp. 1375-1383 ◽

Cited By ~ 1

Author(s):

Haibo Hu ◽

Xiaoyuan Hong ◽

Yuan Zhang ◽

Xiuqun Yang ◽

Wei Liu ◽

...

Keyword(s):

Indian Ocean ◽

El Niño ◽

El Nino ◽

Ocean Warming ◽

Northwest Pacific ◽

Remote Forcing ◽

Foam Model ◽

Indian Ocean Warming ◽

Model Approach

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Historic Yangtze flooding of 2020 tied to extreme Indian Ocean conditions

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2022255118 ◽

2021 ◽

Vol 118 (12) ◽

pp. e2022255118

Author(s):

Zhen-Qiang Zhou ◽

Shang-Ping Xie ◽

Renhe Zhang

Keyword(s):

Indian Ocean ◽

East Asia ◽

El Niño ◽

El Nino ◽

Summer Rainfall ◽

Ocean Warming ◽

Northwest Pacific ◽

Indian Ocean Warming ◽

Yangtze Basin ◽

The Indian Ocean

Heavy monsoon rainfall ravaged a large swath of East Asia in summer 2020. Severe flooding of the Yangtze River displaced millions of residents in the midst of a historic public health crisis. This extreme rainy season was not anticipated from El Niño conditions. Using observations and model experiments, we show that the record strong Indian Ocean Dipole event in 2019 is an important contributor to the extreme Yangtze flooding of 2020. This Indian Ocean mode and a weak El Niño in the Pacific excite downwelling oceanic Rossby waves that propagate slowly westward south of the equator. At a mooring in the Southwest Indian Ocean, the thermocline deepens by a record 70 m in late 2019. The deepened thermocline helps sustain the Indian Ocean warming through the 2020 summer. The Indian Ocean warming forces an anomalous anticyclone in the lower troposphere over the Indo-Northwest Pacific region and intensifies the upper-level westerly jet over East Asia, leading to heavy summer rainfall in the Yangtze Basin. These coupled ocean-atmosphere processes beyond the equatorial Pacific provide predictability. Indeed, dynamic models initialized with observed ocean state predicted the heavy summer rainfall in the Yangtze Basin as early as April 2020.

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Decadal Shift in El Niño Influences on Indo–Western Pacific and East Asian Climate in the 1970s*

Journal of Climate ◽

10.1175/2010jcli3429.1 ◽

2010 ◽

Vol 23 (12) ◽

pp. 3352-3368 ◽

Cited By ~ 176

Author(s):

Shang-Ping Xie ◽

Yan Du ◽

Gang Huang ◽

Xiao-Tong Zheng ◽

Hiroki Tokinaga ◽

...

Keyword(s):

Indian Ocean ◽

El Niño ◽

Rossby Waves ◽

El Nino ◽

East Asian ◽

North Indian Ocean ◽

Ocean Warming ◽

Interdecadal Change ◽

Wind Pattern ◽

The North

Abstract El Niño’s influence on the subtropical northwest (NW) Pacific climate increased after the climate regime shift of the 1970s. This is manifested in well-organized atmospheric anomalies of suppressed convection and a surface anticyclone during the summer (June–August) of the El Niño decay year [JJA(1)], a season when equatorial Pacific sea surface temperature (SST) anomalies have dissipated. In situ observations and ocean–atmospheric reanalyses are used to investigate mechanisms for the interdecadal change. During JJA(1), the influence of the El Niño–Southern Oscillation (ENSO) on the NW Pacific is indirect, being mediated by SST conditions over the tropical Indian Ocean (TIO). The results here show that interdecadal change in this influence is due to changes in the TIO response to ENSO. During the postregime shift epoch, the El Niño teleconnection excites downwelling Rossby waves in the south TIO by anticyclonic wind curls. These Rossby waves propagate slowly westward, causing persistent SST warming over the thermocline ridge in the southwest TIO. The ocean warming induces an antisymmetric wind pattern across the equator, and the anomalous northeasterlies cause the north Indian Ocean to warm through JJA(1) by reducing the southwesterly monsoon winds. The TIO warming excites a warm Kelvin wave in tropospheric temperature, resulting in robust atmospheric anomalies over the NW Pacific that include the surface anticyclone. During the preregime shift epoch, ENSO is significantly weaker in variance and decays earlier than during the recent epoch. Compared to the epoch after the mid-1970s, SST and wind anomalies over the TIO are similar during the developing and mature phases of ENSO but are very weak during the decay phase. Specifically, the southern TIO Rossby waves are weaker, so are the antisymmetric wind pattern and the North Indian Ocean warming during JJA(1). Without the anchor in the TIO warming, atmospheric anomalies over the NW Pacific fail to develop during JJA(1) prior to the mid-1970s. The relationship of the interdecadal change to global warming and implications for the East Asian summer monsoon are discussed.

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A Strengthened Influence of ENSO on August High Temperature Extremes over the Southern Yangtze River Valley since the Late 1980s

Journal of Climate ◽

10.1175/jcli-d-12-00277.1 ◽

2013 ◽

Vol 26 (7) ◽

pp. 2205-2221 ◽

Cited By ~ 41

Author(s):

Kaiming Hu ◽

Gang Huang ◽

Renguang Wu

Keyword(s):

Indian Ocean ◽

El Niño ◽

Yangtze River ◽

El Nino ◽

North Indian Ocean ◽

Yangtze River Valley ◽

Indian Ocean Warming ◽

Upper Level ◽

The Relationship ◽

High Temperature Extremes

Abstract The present study investigates the decadal change in the relationship between China high temperature extremes (HTEs) and El Niño–Southern Oscillation (ENSO). It is found that the relationship between the August HTEs in the southern Yangtze River valley (SYRV) and ENSO has strengthened since the late 1980s. Before the late 1980s, the relationship is weak, whereas, after the late 1980s, the August hot-day numbers in the SYRV region tend to be more than normal during El Niño decaying years. During 1988–2008, El Niño–induced August warm SST anomalies are mainly located in the eastern tropical and north Indian Ocean. As a response to the north Indian Ocean warming, the South Asia high extends eastward, and the SYRV is overlain by upper-level easterly anomalies. The cold horizontal temperature advection induced by upper-level easterly anomalies leads to anomalous descent, which is conducive to the occurrence of HTEs through adiabatic warming. During 1966–86, El Niño–induced August warm SST anomalies are mainly distributed in the equatorial central and southwest tropical Indian Ocean. Corresponding to the equatorial Indian Ocean warming, the ascending motion over the Arabian Sea is enhanced, which leads to an anomalous anticyclone over the Middle East through a Rossby wave–type response and in turn an anomalous cyclone over China through a midlatitude wave pattern. The SYRV is controlled by upper-level westerly anomalies, which is not conducive to the occurrence of HTEs since the corresponding horizontal temperature advection and anomalous vertical motion are weak. As such, the impact of ENSO on August SYRV HTEs is weak before the late 1980s.

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Differential Influences of Teleconnections from the Indian and Pacific Oceans on Rainfall Variability in Southeast Asia

Atmosphere ◽

10.3390/atmos11090886 ◽

2020 ◽

Vol 11 (9) ◽

pp. 886

Author(s):

Abdul Azim Amirudin ◽

Ester Salimun ◽

Fredolin Tangang ◽

Liew Juneng ◽

Muhamad Zuhairi

Keyword(s):

Indian Ocean ◽

Southeast Asia ◽

El Niño ◽

El Nino ◽

Rainfall Variability ◽

June July August ◽

Rainfall Patterns ◽

Negative Impacts ◽

The Individual ◽

June July

This study investigates the individual and combined impacts of El Niño and the positive Indian Ocean Dipole (IOD) on the Southeast Asia (SEA) rainfall variability. Using composite and partial correlation techniques, it is shown that both inter-annual events have individually distinct impacts on the SEA rainfall anomaly distribution. The results showed that the impacts of the co-occurrence of El Niño and IOD events are significant compared to the individual effects of pure El Niño or pure IOD. During June-July-August and September-October-November, the individual impacts of the pure El Niño and IOD events are similar but less significant. Both events caused negative impacts over the southern part of SEA during June-July-August (JJA) and propagated northeastward/eastward during September-October-November (SON). Thus, there are significant negative impacts over the southern part of SEA during the co-occurrence of both events. The differential impacts on the anomalous rainfall patterns are due to the changes in the sea surface temperature (SST) surrounding the region. Additionally, the differences are also related to the anomalous regional atmospheric circulations that interact with the regional SST. The anomalous Walker circulation that connects the Indian Ocean and tropical Pacific Ocean also plays a significant role in determining the regional anomalous rainfall patterns.

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