Seasonal climate summary for the southern hemisphere (spring 2018): positive Indian Ocean Dipole and Australia

AbstractThe 2019 positive Indian Ocean Dipole (IOD) event in the boreal autumn was the most serious IOD event of the century with reports of significant sea surface temperature (SST) changes in the east and west equatorial Indian Ocean. Observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) between 2012 and 2020 are used to study the significant biological dipole response that occurred in the equatorial Indian Ocean following the 2019 positive IOD event. For the first time, we propose, identify, characterize, and quantify the biological IOD. The 2019 positive IOD event led to anomalous biological activity in both the east IOD zone and west IOD zone. The average chlorophyll-a (Chl-a) concentration reached over ~ 0.5 mg m−3 in 2019 in comparison to the climatology Chl-a of ~ 0.3 mg m−3 in the east IOD zone. In the west IOD zone, the biological activity was significantly depressed. The depressed Chl-a lasted until May 2020. The anomalous ocean biological activity in the east IOD zone was attributed to the advection of the higher-nutrient surface water due to enhanced upwelling. On the other hand, the dampened ocean biological activity in the west IOD zone was attributed to the stronger convergence of the surface waters than that in a normal year.

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Impact of the Strong Downwelling (Upwelling) on Small Pelagic Fish Production during the 2016 (2019) Negative (Positive) Indian Ocean Dipole Events in the Eastern Indian Ocean off Java

Climate ◽

10.3390/cli9020029 ◽

2021 ◽

Vol 9 (2) ◽

pp. 29

Author(s):

Jonson Lumban-Gaol ◽

Eko Siswanto ◽

Kedarnath Mahapatra ◽

Nyoman Metta Nyanakumara Natih ◽

I Wayan Nurjaya ◽

...

Keyword(s):

Indian Ocean ◽

Indian Ocean Dipole ◽

Pelagic Fish ◽

Eastern Indian Ocean ◽

Fish Production ◽

Small Pelagic Fish ◽

Field Surveys ◽

Chl A ◽

Positive Indian Ocean Dipole ◽

The Impact

Although researchers have investigated the impact of Indian Ocean Dipole (IOD) phases on human lives, only a few have examined such impacts on fisheries. In this study, we analyzed the influence of negative (positive) IOD phases on chlorophyll a (Chl-a) concentrations as an indicator of phytoplankton biomass and small pelagic fish production in the eastern Indian Ocean (EIO) off Java. We also conducted field surveys in the EIO off Palabuhanratu Bay at the peak (October) and the end (December) of the 2019 positive IOD phase. Our findings show that the Chl-a concentration had a strong and robust association with the 2016 (2019) negative (positive) IOD phases. The negative (positive) anomalous Chl-a concentration in the EIO off Java associated with the negative (positive) IOD phase induced strong downwelling (upwelling), leading to the preponderant decrease (increase) in small pelagic fish production in the EIO off Java.

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Two-year consecutive concurrences of positive Indian Ocean Dipole and Central Pacific El Niño preconditioned the 2019/2020 Australian “black summer” bushfires

Geoscience Letters ◽

10.1186/s40562-020-00168-2 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Guojian Wang ◽

Wenju Cai

Keyword(s):

Indian Ocean ◽

El Niño ◽

Indian Ocean Dipole ◽

El Nino ◽

Greenhouse Warming ◽

Central Pacific ◽

Central Pacific El Niño ◽

Positive Indian Ocean Dipole ◽

The Future ◽

Rainfall Anomalies

Abstract The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.

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Triggering the Indian Ocean Dipole from the Southern Hemisphere

10.5194/egusphere-egu21-3655 ◽

2021 ◽

Author(s):

Lian-Yi Zhang ◽

Yan Du ◽

Wenju Cai ◽

Zesheng Chen ◽

Tomoki Tozuka ◽

...

Keyword(s):

Indian Ocean ◽

Southern Hemisphere ◽

Indian Ocean Dipole ◽

Southern Oscillation ◽

Southern Annular Mode ◽

Triggering Mechanism ◽

Phase Development ◽

The Indian Ocean ◽

High System ◽

The Tropics

<p>This study identifies a new triggering mechanism of the Indian Ocean Dipole (IOD) from the Southern Hemisphere. This mechanism is independent from the El Ni&#241;o/Southern Oscillation (ENSO) and tends to induce the IOD before its canonical peak season. The joint effects of this mechanism and ENSO may explain different lifetimes and strengths of the IOD. During its positive phase, development of sea surface temperature cold anomalies commences in the southern Indian Ocean, accompanied by an anomalous subtropical high system and anomalous southeasterly winds. The eastward movement of these anomalies enhances the monsoon off Sumatra-Java during May-August, leading to an early positive IOD onset. The pressure variability in the subtropical area is related with the Southern Annular Mode, suggesting a teleconnection between high-latitude and mid-latitude climate that can further affect the tropics. To include the subtropical signals may help model prediction of the IOD event.</p>

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Stabilised frequency of extreme positive Indian Ocean Dipole under 1.5 °C warming

Nature Communications ◽

10.1038/s41467-018-03789-6 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 15

Author(s):

Wenju Cai ◽

Guojian Wang ◽

Bolan Gan ◽

Lixin Wu ◽

Agus Santoso ◽

...

Keyword(s):

Indian Ocean ◽

Indian Ocean Dipole ◽

Positive Indian Ocean Dipole

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Coastal upwelling events along the southern coast of Java during the 2008 positive Indian Ocean Dipole

Journal of Oceanography ◽

10.1007/s10872-018-0475-z ◽

2018 ◽

Vol 74 (5) ◽

pp. 499-508 ◽

Cited By ~ 1

Author(s):

T. Horii ◽

I. Ueki ◽

K. Ando

Keyword(s):

Indian Ocean ◽

Indian Ocean Dipole ◽

Coastal Upwelling ◽

Southern Coast ◽

Positive Indian Ocean Dipole

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Seasonal Responses of Precipitation in China to El Niño and Positive Indian Ocean Dipole Modes

Atmosphere ◽

10.3390/atmos10070372 ◽

2019 ◽

Vol 10 (7) ◽

pp. 372 ◽

Cited By ~ 4

Author(s):

Chunxiang Li ◽

Tianbao Zhao

Keyword(s):

Indian Ocean ◽

El Niño ◽

Indian Ocean Dipole ◽

North China ◽

El Nino ◽

Southern Oscillation ◽

Southern China ◽

Northwestern China ◽

Positive Indian Ocean Dipole ◽

Seasonal Responses

Using composite, regular, and partial regression analyses in the six consecutive seasons from spring of the El Niño–Southern Oscillation (ENSO)-/Indian Ocean Dipole (IOD)-developing year through summer following the ENSO/IOD mature phase, the individual and combined impacts of El Niño and positive Indian Ocean Dipole (pIOD) on the evolution of precipitation in China are diagnosed for the period 1950–2013. It is shown that the seasonal responses of precipitation in China to El Niño and pIOD events, and their relationship with the large-scale atmospheric circulations, differ from one season to another. For the pure El Niño years, there is a seasonal reversal of precipitation over southeastern and northwestern China, with deficient precipitation occurring in these two regions before the onset of anomalous wet conditions in the developing autumn. Meanwhile, North China tends to be drier than normal in the developing seasons, but wetter than normal in the decaying seasons. For the pure pIOD events, southern China suffers a precipitation deficit (surplus) in the developing spring (summer and autumn). Furthermore, both North China and northwestern China experience excessive precipitation in the developing autumn and decaying summer. In addition, there is reduced precipitation in northeastern China during both the developing and decaying summers, whereas increased precipitation occurs in the developing autumn and decaying winter. For the combined years, southern China experiences enhanced moisture supply and suffers from increased precipitation from the developing summer through the subsequent spring, but reduced precipitation in the developing spring and decaying summer. Similar to the pure El Niño, northwestern (North) China becomes wetter than normal after the developing summer (autumn) in the combined years. In general, the ENSO/IOD-related precipitation variability could be explained by the associated anomaly circulations.

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