Role of tropical Indian Ocean air-sea interactions in modulating Indian summer monsoon in a coupled model

Abstract The biennial variability is a large component of year-to-year variations in the Indian summer monsoon (ISM). Previous studies have shown that El Niño–Southern Oscillation (ENSO) plays an important role in the biennial variability of the ISM. The present study investigates the role of the Indian Ocean in the biennial transition of the ISM when the Pacific ENSO is absent. The influence of the Indian and Pacific Oceans on the biennial transition between the ISM and the Australian summer monsoon (ASM) is also examined. Controlled numerical experiments with a coupled general circulation model (CGCM) are used to address the above two issues. The CGCM captures the in-phase ISM to ASM transition (i.e., a wet ISM followed by a wet ASM or a dry ISM followed by a dry ASM) and the out-of-phase ASM to ISM transition (i.e., a wet ASM followed by a dry ISM or a dry ASM followed by a wet ISM). These transitions are more frequent than the out-of-phase ISM to ASM transition and the in-phase ASM to ISM transition in the coupled model, consistent with observations. The results of controlled coupled model experiments indicate that both the Indian and Pacific Ocean air–sea coupling are important for properly simulating the biennial transition between the ISM and ASM in the CGCM. The biennial transition of the ISM can occur through local air–sea interactions in the north Indian Ocean when the Pacific ENSO is suppressed. The local sea surface temperature (SST) anomalies induce the Indian monsoon transition through low-level moisture convergence. Surface evaporation anomalies, which are largely controlled by surface wind speed changes, play an important role for SST changes. Different from local air–sea interaction mechanisms proposed in previous studies, the atmospheric feedback is not strong enough to reverse the SST anomalies immediately at the end of the monsoon season. Instead, the reversal of the SST anomalies is accomplished in the spring of the following year, which in turn leads to the Indian monsoon transition.

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Anatomy of the Indian Summer Monsoon and ENSO relationships in state-of-the-art CGCMs: role of the tropical Indian Ocean

Climate Dynamics ◽

10.1007/s00382-020-05484-z ◽

2020 ◽

Author(s):

Pascal Terray ◽

K. P. Sooraj ◽

Sébastien Masson ◽

Chloé Prodhomme

Keyword(s):

Indian Ocean ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

State Of The Art ◽

Tropical Indian Ocean

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Possible Role of the Indian Ocean in the Out-of-Phase Transition of the Australian to Indian Summer Monsoon

Journal of Climate ◽

10.1175/2008jcli2602.1 ◽

2009 ◽

Vol 22 (7) ◽

pp. 1834-1849 ◽

Cited By ~ 11

Author(s):

Renguang Wu

Keyword(s):

Indian Ocean ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

Tropical Indian Ocean ◽

North Indian Ocean ◽

The North ◽

The Indian Ocean ◽

Sst Anomalies ◽

Type Of Transition

Abstract The present study investigates processes for out-of-phase transitions from the Australian summer monsoon (ASM) to the Indian summer monsoon (ISM). Two types of out-of-phase ASM-to-ISM transitions have been identified, depending on the evolution of the Pacific El Niño–Southern Oscillation (ENSO) events. The first type of transition is accompanied by a phase switch of ENSO in boreal spring to early summer. In the second type of transition, ENSO maintains its phase through boreal summer. The direct ENSO forcing plays a primary role for the first type of out-of-phase ASM-to-ISM transition, with complementary roles from the north Indian Ocean sea surface temperature (SST) anomalies that are partly induced by ENSO. The second type of out-of-phase ASM-to-ISM transition involves air–sea interaction processes in the tropical Indian Ocean that generate the north Indian Ocean SST anomalies and contribute to the monsoon transition. The initiation of tropical Indian Ocean air–sea interaction is closely related to ENSO in observations, but could also occur without ENSO according to a coupled general circulation model simulation. Results of numerical simulations substantiate the role of the Indian Ocean air–sea interaction in the out-of-phase ASM-to-ISM transition.

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Barotropic Energy Conversion During Indian Summer Monsoon: Implication of Central Indian Ocean Mode Simulation in CMIP6

10.21203/rs.3.rs-715759/v1 ◽

2021 ◽

Author(s):

Jianhuang Qin ◽

Lei Zhou ◽

Ze Meng ◽

Baosheng Li ◽

Tao Lian ◽

...

Keyword(s):

Indian Ocean ◽

Kinetic Energy ◽

Energy Conversion ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

Climate Models ◽

Intraseasonal Variability ◽

Coupled Model ◽

Tropical Indian Ocean ◽

Central Indian Ocean

Abstract The simulation and prediction of the Indian summer monsoon (ISM) and its intraseasonal component in climate models remain a grand scientific challenge for models. Recently, an intraseasonal mode was proposed over the tropical Indian Ocean, named central Indian Ocean (CIO) mode. The CIO mode index and with monsoon intraseasonal oscillations (MISO) have a high correlation. In this study, the simulations of the CIO mode in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) models are examined. Although the coupled ocean-atmosphere feedbacks associated with the CIO mode are not fully reproduced, the results show that a better depiction of the CIO mode in CMIP6 models is favorable for a better simulation of northward-propagating MISO and heavy rainfall during the ISM. Dynamic diagnostics unveil that the rendition of the CIO mode is dominated by kinetic energy conversion from the background to the intraseasonal variability. Furthermore, kinetic energy conversion is controlled by the meridional shear of background zonal winds (\(\frac{\partial \stackrel{-}{u}}{\partial y}\)), which is underestimated in most CMIP6 models, leading to a weak barotropic instability. As a result, a better simulation of \(\frac{\partial \stackrel{-}{u}}{\partial y}\) is required for improving the CIO mode simulation in climate models, which helps to improve the simulation and prediction skill of northward-propagating MISO and monsoonal precipitation.

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