scholarly journals Independence of SST skewness from thermocline feedback in the eastern equatorial Indian Ocean

2010 ◽  
Vol 37 (11) ◽  
pp. n/a-n/a ◽  
Author(s):  
Chi-Cherng Hong ◽  
Tim Li
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Thermocline Feedback ◽  
Eastern Equatorial Indian Ocean

Indian Ocean Dipole Response to Global Warming in the CMIP5 Multimodel Ensemble*

2013 ◽  
Vol 26 (16) ◽  
pp. 6067-6080 ◽  
Author(s):  
Xiao-Tong Zheng ◽  
Shang-Ping Xie ◽  
Yan Du ◽  
Lin Liu ◽  
Gang Huang ◽  
...  
Keyword(s):  
Global Warming ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Coupled Model ◽  
Equatorial Indian Ocean ◽  
Easterly Wind ◽  
Thermocline Feedback ◽  
Intercomparison Project ◽  
Eastern Equatorial Indian Ocean ◽  
Dipole Response

Abstract The response of the Indian Ocean dipole (IOD) mode to global warming is investigated based on simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In response to increased greenhouse gases, an IOD-like warming pattern appears in the equatorial Indian Ocean, with reduced (enhanced) warming in the east (west), an easterly wind trend, and thermocline shoaling in the east. Despite a shoaling thermocline and strengthened thermocline feedback in the eastern equatorial Indian Ocean, the interannual variance of the IOD mode remains largely unchanged in sea surface temperature (SST) as atmospheric feedback and zonal wind variance weaken under global warming. The negative skewness in eastern Indian Ocean SST is reduced as a result of the shoaling thermocline. The change in interannual IOD variance exhibits some variability among models, and this intermodel variability is correlated with the change in thermocline feedback. The results herein illustrate that mean state changes modulate interannual modes, and suggest that recent changes in the IOD mode are likely due to natural variations.

Photosynthetic physiologies of phytoplankton in the eastern equatorial Indian Ocean during the spring inter-monsoon

2019 ◽  
Vol 38 (6) ◽  
pp. 83-91 ◽  
Author(s):  
Chao Yuan ◽  
Zongjun Xu ◽  
Xuelei Zhang ◽  
Qinsheng Wei ◽  
Huiwu Wang ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

scholarly journals Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

2008 ◽  
Vol 113 (C7) ◽  
Author(s):  
Tomomichi Ogata ◽  
Hideharu Sasaki ◽  
V. S. N. Murty ◽  
M. S. S. Sarma ◽  
Yukio Masumoto
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

Indian Ocean Dipole Response to Global Warming: Analysis of Ocean–Atmospheric Feedbacks in a Coupled Model*

2010 ◽  
Vol 23 (5) ◽  
pp. 1240-1253 ◽  
Author(s):  
Xiao-Tong Zheng ◽  
Shang-Ping Xie ◽  
Gabriel A. Vecchi ◽  
Qinyu Liu ◽  
Jan Hafner
Keyword(s):  
Global Warming ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
General Circulation ◽  
Equatorial Indian Ocean ◽  
Thermocline Depth ◽  
Easterly Wind ◽  
Thermocline Feedback ◽  
Ocean Atmosphere ◽  
Atmospheric Feedbacks

Abstract Low-frequency modulation and change under global warming of the Indian Ocean dipole (IOD) mode are investigated with a pair of multicentury integrations of a coupled ocean–atmosphere general circulation model: one under constant climate forcing and one forced by increasing greenhouse gas concentrations. In the unforced simulation, there is significant decadal and multidecadal modulation of the IOD variance. The mean thermocline depth in the eastern equatorial Indian Ocean (EEIO) is important for the slow modulation, skewness, and ENSO correlation of the IOD. With a shoaling (deepening) of the EEIO thermocline, the thermocline feedback strengthens, and this leads to an increase in IOD variance, a reduction of the negative skewness of the IOD, and a weakening of the IOD–ENSO correlation. In response to increasing greenhouse gases, a weakening of the Walker circulation leads to easterly wind anomalies in the equatorial Indian Ocean; the oceanic response to weakened circulation is a thermocline shoaling in the EEIO. Under greenhouse forcing, the thermocline feedback intensifies, but surprisingly IOD variance does not. The zonal wind anomalies associated with IOD are found to weaken, likely due to increased static stability of the troposphere from global warming. Linear model experiments confirm this stability effect to reduce circulation response to a sea surface temperature dipole. The opposing changes in thermocline and atmospheric feedbacks result in little change in IOD variance, but the shoaling thermocline weakens IOD skewness. Little change under global warming in IOD variance in the model suggests that the apparent intensification of IOD activity during recent decades is likely part of natural, chaotic modulation of the ocean–atmosphere system or the response to nongreenhouse gas radiative changes.

scholarly journals Response of the South Asian Summer Monsoon to Global Warming: Mean and Synoptic Systems*

2009 ◽  
Vol 22 (4) ◽  
pp. 1014-1036 ◽  
Author(s):  
Markus Stowasser ◽  
H. Annamalai ◽  
Jan Hafner
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Equatorial Indian Ocean ◽  
South Asian Summer Monsoon ◽  
Eastern Equatorial Indian Ocean ◽  
Asian Summer ◽  
The Mean ◽  
Gfdl Model

Abstract Recent diagnostics with the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1), coupled model’s twentieth-century simulations reveal that this particular model demonstrates skill in capturing the mean and variability associated with the South Asian summer monsoon precipitation. Motivated by this, the authors examine the future projections of the mean monsoon and synoptic systems in this model’s simulations in which quadrupling of CO2 concentrations are imposed. In a warmer climate, despite a weakened cross-equatorial flow, the time-mean precipitation over peninsular parts of India increases by about 10%–15%. This paradox is interpreted as follows: the increased precipitation over the equatorial western Pacific forces an anomalous descending circulation over the eastern equatorial Indian Ocean, the two regions being connected by an overturning mass circulation. The spatially well-organized anomalous precipitation over the eastern equatorial Indian Ocean forces twin anticyclones as a Rossby wave response in the lower troposphere. The southern component of the anticyclone opposes and weakens the climatological cross-equatorial monsoon flow. The patch of easterly anomalies centered in the southern Arabian Sea is expected to deepen the thermocline north of the equator. Both these factors limit the coastal upwelling along Somalia, resulting in local sea surface warming and eventually leading to a local maximum in evaporation over the southern Arabian Sea. It is shown that changes in SST are predominantly responsible for the increase in evaporation over the southern Arabian Sea. The diagnostics suggest that in addition to the increased CO2-induced rise in temperature, evaporation, and atmospheric moisture, local circulation changes in the monsoon region further increase SST, evaporation, and atmospheric moisture, leading to increased rainfall over peninsular parts of India. This result implies that accurate observation of SST and surface fluxes over the Indian Ocean is of urgent need to understand and monitor the response of the monsoon in a warming climate. To understand the regional features of the rainfall changes, the International Pacific Research Center (IPRC) Regional Climate Model (RegCM), with three different resolution settings (0.5° × 0.5°, 0.75° × 0.75°, and 1.0° × 1.0°), was integrated for 20 yr, with lateral and lower boundary conditions taken from the GFDL model. The RegCM solutions confirm the major results obtained from the GFDL model but also capture the orographic nature of monsoon precipitation and regional circulation changes more realistically. The hypothesis that in a warmer climate, an increase in troposphere moisture content favors more intense monsoon depressions is tested. The GFDL model does not reveal any changes, but solutions from the RegCM suggest a statistically significant increase in the number of storms that have wind speeds of 15–20 m s−1 or greater, depending on the resolution employed. Based on these regional model solutions a possible implication is that in a CO2-richer climate an increase in the number of flood days over central India can be expected. The model results obtained here, though plausible, need to be taken with caution since even in this “best” model systematic errors still exist in simulating some aspects of the tropical and monsoon climates.

Nutrient characteristics of the water masses and their seasonal variability in the eastern equatorial Indian Ocean

2010 ◽  
Vol 70 (3-4) ◽  
pp. 272-282 ◽  
Author(s):  
S. Sardessai ◽  
Suhas Shetye ◽  
M.V. Maya ◽  
K.R. Mangala ◽  
S. Prasanna Kumar
Keyword(s):  
Indian Ocean ◽  
Seasonal Variability ◽  
Equatorial Indian Ocean ◽  
Water Masses ◽  
Eastern Equatorial Indian Ocean

Importance of wind variations and intersecting waveguides near Sri Lanka for the intraseasonal sea level variability along the west coast of India

2020 ◽  
Author(s):  
Iyyappan Suresh ◽  
Jerome Vialard ◽  
Matthieu Lengaigne ◽  
Takeshi Izumo ◽  
Muraleedharan Pillathu Moolayil
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Sea Level ◽  
Bay Of Bengal ◽  
West Coast ◽  
Equatorial Indian Ocean ◽  
Direct Connection ◽  
Local Wind ◽  
The West ◽  
Eastern Equatorial Indian Ocean

<p>Remote wind forcing plays a strong role in the Northern Indian Ocean, where oceanic anomalies can travel long distances within the coastal waveguide. Previous studies for instance emphasized that remote equatorial forcing is the main driver of the sea level and currents intraseasonal variability along the west coast of India (WCI). Until now, the main pathway for this connection between the equatorial and coastal waveguides was thought to occur in the eastern equatorial Indian Ocean, through coastal Kelvin waves that propagate around the Bay of Bengal rim and then around Sri Lanka to the WCI. Using a linear, continuously stratified ocean model, the present study demonstrates that two other mechanisms in fact dominate. First, the equatorial waveguide also intersects the coastal waveguide at the southern tip of India and Sri Lanka, creating a direct connection between the equator and WCI. Rossby waves reflected from the eastern equatorial Indian Ocean boundary indeed have a sufficiently wide meridional scale to induce a pressure signal at the Sri Lankan coast, which eventually propagates to the WCI as a coastal Kelvin wave. Second, local wind variations in the vicinity of Sri Lanka generate strong intraseasonal signals, which also propagate to the WCI along the same path. Sensitivity experiments indicate that these two new mechanisms (direct equatorial connection and local wind variations near Sri Lanka) dominate the WCI intraseasonal sea level variability, with the “classical” pathway around the Bay of Bengal only coming next. Other contributions (Bay of Bengal forcing, local WCI forcing) are much weaker.</p><p>We further show that the direct connection between the equatorial waveguide and WCI is negligible at seasonal timescale, but not at interannual timescales where it contributes to the occurrence of anoxic events. By providing an improved understanding of the mechanisms that control the WCI thermocline and oxycline variability, our results could have socio-economic implications for regional fisheries and ecosystems.</p>

scholarly journals A model study of the seasonal variability and formation mechanisms of the barrier layer in the eastern equatorial Indian Ocean

2002 ◽  
Vol 107 (C12) ◽  
pp. SRF 18-1-SRF 18-20 ◽  
Author(s):  
Sébastien Masson ◽  
Pascale Delecluse ◽  
Jean-Philippe Boulanger ◽  
Christophe Menkes
Keyword(s):  
Indian Ocean ◽  
Barrier Layer ◽  
Seasonal Variability ◽  
Equatorial Indian Ocean ◽  
Formation Mechanisms ◽  
Model Study ◽  
Eastern Equatorial Indian Ocean
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