| |
| |
|
|
|
|
| |
 |
The Ocean and Atmosphere in the Maritime Continent and Their Impacts
|
| |
|
|
Oceanic Intraseasonal Variabilities associated with Central Indian Ocean Mode
Wednesday 9th @ 1010-1030, Conference Room 4
Lei Zhou* , Institute of Oceanography, Shanghai Jiao Tong University
Ze Meng, Second Institute of Oceanography, SOA
Presenter Email: zhoulei1588@sjtu.edu.cn |
| The intraseasonal variabilities (ISVs) with a period between 30 and 60 days are pronounced over the tropical Indian Ocean, especially over the eastern Indian Ocean, where is the exit region of the Indonesian Throughflow (ITF). It is well known that the Madden-Julian Oscillation (MJO) is the dominant component of ISVs in the atmosphere. As a result, the existing studies on the oceanic ISVs over tropical Indian Ocean mainly focus on the oceanic responses to the atmospheric forcing accompanied with the MJO. The air-sea interaction over the maritime continent on intraseasonal timescales also focus on the processes related to the MJO. The MJO propagates eastwards. Correspondingly, the eastward propagation of intraseasonal SST anomalies and intraseasonal ocean currents have been captured by observations. Their interactions with the maritime continent are also diagnosed in many previous studies.
Recently, a Central Indian Ocean (CIO) mode is proposed on the intraseasonal timescales. Associated with the CIO mode, the oceanic ISVs show quite different features from the traditional ones, which are mainly attributable to the oceanic responses to the atmospheric forcing. The composite intraseasonal SST anomalies during the positive CIO mode propagate westward, instead of eastward, which is opposite to the direction of either the equatorial Kelvin waves or the MJO in the atmosphere. In addition, the composite net surface heat flux heat fluxes are not fully consistent with the SST variabilities, which indicates that the air-sea heat flux alone cannot explain the intraseasonal SST anomalies. Moreover, the composite intraseasonal sea surface height (SSH) anomalies show an eastward propagation. The inconsistent behaviors of the SST anomalies and SSH anomalies imply a separation between the dynamics and thermodynamics in the ocean, which is an omen for complex oceanic processes for the oceanic ISVs associated with the CIO mode. Overall, the westward-propagating intraseasonal SST anomalies and the oceanic dynamics behind are the target of this study.
A mechanism analogous to the recharge-discharge theory for ENSO is proposed in this study, but for the ISVs. The upwelling off the Sumatra is a key component of the whole process. As a result, it is expected that the variabilities associated with the CIO mode over the eastern Indian Ocean may provide a new avenue to connect the ISVs over the maritime continent and the tropical Indian Ocean. |
|
|
|
|
|
|
|
|