scholarly journals Interdecadal Indian Ocean Basin Mode Driven by Interdecadal Pacific Oscillation: A Season-Dependent Growth Mechanism

2019 ◽  
Vol 32 (7) ◽  
pp. 2057-2073 ◽  
Author(s):  
Yu Huang ◽  
Bo Wu ◽  
Tim Li ◽  
Tianjun Zhou ◽  
Bo Liu
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Ocean Basin ◽  
Heat Fluxes ◽  
Boreal Winter ◽  
Interdecadal Pacific Oscillation ◽  
Indian Ocean Basin Mode ◽  
Remote Forcing ◽  
Basin Mode

The interdecadal variability of basinwide sea surface temperature anomalies (SSTAs) in the tropical Indian Ocean (TIO), referred to as the interdecadal Indian Ocean basin mode (ID-IOBM), is caused by remote forcing of the interdecadal Pacific oscillation (IPO), as demonstrated by the observational datasets and tropical Pacific pacemaker experiments of the Community Earth System Model (CESM). It is noted that the growth of the ID-IOBM shows a season-dependent characteristic, with a maximum tendency of mixed layer heat anomalies occurring in early boreal winter. Three factors contribute to this maximum tendency. In response to the positive IPO forcing, the eastern TIO is covered by the descending branch of the anomalous Walker circulation. Thus, the convection over the southeastern TIO is suppressed, which increases local downward shortwave radiative fluxes. Meanwhile, the equatorial easterly anomalies to the west of the suppressed convection weaken the background mean westerly and thus decrease the upward latent heat fluxes over the equatorial Indian Ocean. Third, anomalous westward Ekman currents driven by the equatorial easterly anomalies advect climatological warm water westward and thus warm the western TIO. In summer, the TIO is out of the control of the positive IPO remote forcing. The ID-IOBM gradually decays due to the Newtonian damping effect.

Understanding the Weakening Relationship of the Pacific Decadal Oscillation and Indian Ocean Basin Mode During Boreal Winter

2021 ◽  
Author(s):  
Jin-Sil Hong ◽  
Sang-Wook Yeh ◽  
Young-Min Yang ◽  
Young-Kwon Lim ◽  
Kyu-Myong Kim
Keyword(s):  
Indian Ocean ◽  
Pacific Decadal Oscillation ◽  
Climate Model ◽  
Ocean Basin ◽  
Boreal Winter ◽  
Indian Ocean Basin Mode ◽  
The Pacific ◽  
Basin Mode ◽  
Relationship Of

Abstract While it is known that the Pacific Decadal Oscillation (PDO) leads the Indian Ocean Basin Mode (IOBM) with the same phase via the atmospheric bridge, we found that the relationship of PDO-IOBM during boreal winter is not stationary. Here, we investigated the PDO-IOBM relationship changes on low-frequency timescales by analyzing the observations, a long-term simulation of climate model with its large ensembles as well as the pacemaker experiments. A long-term simulation of climate model with its large ensemble simulations indicated that the non-stationary relationship of PDO-IOBM is intrinsic in a climate system and it could be at least partly due to internal climate variability. In details, we compared the PDO structures during the entire period with those during the period when the PDO-IOBM relationship was weak (i.e., 1976-2006). We found that the structures of sea surface temperature (SST) as well as its associated tropical Pacific convective forcing during the negative phase of PDO for 1976-2006 are far away from the typical structures of the negative PDO phase during the entire period, which were responsible for the weakening relationship of the PDO-IOBM in the observation. The results of the two pacemaker experiments support that a non-stationary relationship of PDO-IOBM is primarily due to the SST forcing in the Pacific.

scholarly journals Two Distinct Modes of Tropical Indian Ocean Precipitation in Boreal Winter and Their Impacts on Equatorial Western Pacific*

2012 ◽  
Vol 25 (3) ◽  
pp. 921-938 ◽  
Author(s):  
Bo Wu ◽  
Tianjun Zhou ◽  
Tim Li
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Onset Time ◽  
Tropical Indian Ocean ◽  
Ocean Basin ◽  
Western Pacific ◽  
Boreal Winter ◽  
Indian Ocean Basin Mode ◽  
Basin Scale

Abstract The observational analysis reveals two distinct precipitation modes, the zonal dipole (DP) mode and the monopole (MP) mode, in the tropical Indian Ocean (TIO) during the El Niño mature winter, even though sea surface temperature anomalies (SSTAs) have a similar basinwide warming pattern [referred to as the Indian Ocean basin mode (IOBM)]. The formation of the two precipitation modes depends on the distinct evolutions of the SSTA in the tropical Pacific and Indian Ocean. Both of the precipitation modes are preceded by an Indian Ocean dipole (IOD). The IOD associated with the DP mode developed in late summer and was triggered by Pacific El Niño through a “Sumatra–Philippine pattern.” The IOD associated with the MP mode developed in early summer when the Pacific SSTAs were still normal. The different IOD onset time leads to salient differences in subsequent evolution including the transfer of a dipole SST pattern to a basinwide pattern. As a result, in the boreal winter, the zonal SSTA gradient associated with the DP mode is much stronger than that associated with the MP mode. The strong SSTA zonal gradient associated with the DP mode drives an anomalous Walker circulation in the TIO, while the nearly uniform warm SSTA associated with the MP mode forces a basin-scale upward motion. The two modes have opposite impacts on the zonal wind over the equatorial western Pacific, with anomalous westerly (easterly) occurring during the DP (MP) mode, and thus they may have distinct impacts on El Niño evolution.

Decadal Modulation of the ENSO-Indian Ocean Basin Warming relationship during the decaying summer by the Interdecadal Pacific Oscillation

2021 ◽  
pp. 1-50
Author(s):  
Fangyu Liu ◽  
Wenjun Zhang ◽  
Fei-Fei Jin ◽  
Suqiong Hu
Keyword(s):  
Indian Ocean ◽  
Southern Oscillation ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Seasonal Prediction ◽  
Ocean Basin ◽  
Interdecadal Pacific Oscillation ◽  
Enso Events ◽  
Decadal Modulation ◽  
Sst Anomalies

AbstractMany previous studies have shown that an Indian Ocean basin warming (IOBW) occurs usually during El Niño-Southern Oscillation (ENSO) decaying spring to summer seasons through modifying the equatorial zonal circulation. Decadal modulation associated with the Interdecadal Pacific Oscillation (IPO) is further investigated here to understand the nonstationary ENSO-IOBW relationship during ENSO decaying summer (July-August-September, JAS). During the positive IPO phase, significant warm sea surface temperature (SST) anomalies are observed over the tropical Indian Ocean in El Niño decaying summers and vice versa for La Niña events, while these patterns are not well detected in the negative IPO phase. Different decaying speeds of ENSO associated with the IPO phase, largely controlled by both zonal advective and thermocline feedbacks, are suggested to be mainly responsible for these different ENSO-IOBW relationships. In contrast to ENSO events in the negative IPO phase, the ones in the positive IPO phase display a slower decaying speed and delay their transitions both from a warm to a cold state and a cold to a warm state. The slower decay of El Niño and La Niña thereby helps to sustain the teleconnection forcing over the equatorial Indian Ocean and corresponding SST anomalies there can persist into summer. This IPO modulation of the ENSO-IOBW relationship carries important implications for the seasonal prediction of the Indian Ocean SST anomalies and associated summer climate anomalies.

A study of biases in simulation of the Indian Ocean basin mode and its capacitor effect in CMIP3/CMIP5 models

2015 ◽  
Vol 46 (1-2) ◽  
pp. 205-226 ◽  
Author(s):  
Weichen Tao ◽  
Gang Huang ◽  
Kaiming Hu ◽  
Hainan Gong ◽  
Guanhuan Wen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Ocean Basin ◽  
Cmip5 Models ◽  
Indian Ocean Basin Mode ◽  
Basin Mode ◽  
The Indian Ocean

Interdecadal Strengthening in the Independent Relationship Between the East Asian Summer Monsoon and the Indian Ocean Basin Mode around the Early 1990s

2021 ◽  
pp. 1-42
Author(s):  
KUI LIU ◽  
LIAN-TONG ZHOU ◽  
ZHIBIAO WANG ◽  
YONG LIU ◽  
XIAOXUE YIN
Keyword(s):  
Indian Ocean ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Ocean Basin ◽  
Indian Ocean Basin Mode ◽  
Basin Mode ◽  
The Indian Ocean ◽  
Asian Summer ◽  
The Relationship

AbstractThis study conducts correlation and regression analyses of the JRA-55 reanalysis data and observational rainfall datasets from China’s National Climate Center. The analyses reveal that interdecadal enhancement in the relationship between the East Asian summer monsoon (EASM) and the Indian Ocean Basin mode (IOBM) after the early 1990s, and the diminished correlation between the EASM and the Niño-3 index. The analyses also reveal that the relationship between EASM-related rainfall/circulation with IOBM also experienced an interdecadal shift at the same time. During the first epoch (1977–1989), EASM-related rainfall was correlated significantly with the Niño-3 index, and accompanied by a Pacific–Japan-like anomaly pattern of horizontal winds. In a subsequent epoch (1994–2014), EASM-related rainfall was correlated significantly with IOBM, and accompanied by a meridional dipole pattern in the horizontal winds. After the 1990s, IOBM exerted influence on EASM through land–sea thermal contrast, and the critical land area was the region 33°–47°N, 110°–140°E. The interdecadal strengthening in the EASM–IOBM linkage around the early 1990s may be attributable to a faster rate of decay of El Niño after the 1990s.

Linking Observations of the Asian Monsoon to the Indian Ocean SST: Possible Roles of Indian Ocean Basin Mode and Dipole Mode

2010 ◽  
Vol 23 (21) ◽  
pp. 5889-5902 ◽  
Author(s):  
Jianling Yang ◽  
Qinyu Liu ◽  
Zhengyu Liu
Keyword(s):  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Summer Monsoon ◽  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Ocean Basin ◽  
Indian Ocean Basin Mode ◽  
Basin Mode ◽  
The Indian Ocean ◽  
Asian Summer

Abstract The authors investigate the relationship between sea surface temperature (SST) in the tropical Indian Ocean (TIO) and the seasonal atmosphere circulation in the Asian monsoon region (AMR) using the maximum covariance analyses (MCAs). The results show that the Asian monsoon circulation is significantly correlated with two dominant SST anomaly (SSTA) modes: the Indian Ocean Basin mode (IOB) and the Indian Ocean dipole mode (IOD). The peak SSTA of the IOB appears in spring and has a much stronger relationship with the Asian summer monsoon than the peak of the IOD does, whereas the peak SSTA for the IOD appears in fall and shows a stronger link to the Asian winter monsoon than to the Asian summer monsoon. In addition, the IOB in spring has a relatively stronger link with the atmospheric circulation in summer than in other seasons. The large-scale atmospheric circulation and SSTA patterns of the covariability of the first two dominant MCA modes are described. For the first MCA mode, a warm IOB, persists from spring to summer, and the atmospheric circulation is enhanced by the establishment of the climatological summer monsoon. The increased evaporative moisture associated with the warm IOB is transported to South Asia by the climatological summer monsoon, which increases the moisture convergence toward this region, leading to a significant increase in summer monsoon precipitation. For the second MCA mode, a positive IOD possibly corresponds to a weaker Indian winter monsoon and more precipitation over the southwestern and eastern equatorial TIO.

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