Evaluation of Interannual Simulations and Indian Ocean Dipole Events During 2000–2014 from a Basin Scale General Circulation Model

2018 ◽  
Vol 175 (12) ◽  
pp. 4579-4603 ◽  
Author(s):  
K. K. Sandeep ◽  
Vimlesh Pant
Keyword(s):  
Indian Ocean ◽  
General Circulation Model ◽  
Indian Ocean Dipole ◽  
General Circulation ◽  
Circulation Model ◽  
Basin Scale

scholarly journals Termination of Indian Ocean Dipole Events in a Coupled General Circulation Model

2007 ◽  
Vol 20 (13) ◽  
pp. 3018-3035 ◽  
Author(s):  
Suryachandra A. Rao ◽  
Sebastien Masson ◽  
Jing-Jia Luo ◽  
Swadhin K. Behera ◽  
Toshio Yamagata
Keyword(s):  
Indian Ocean ◽  
Solar Radiation ◽  
General Circulation Model ◽  
Indian Ocean Dipole ◽  
General Circulation ◽  
Circulation Model ◽  
Equatorial Indian Ocean ◽  
Coupled General Circulation Model ◽  
Zonal Winds ◽  
Budget Analysis

Abstract Using 200 yr of coupled general circulation model (CGCM) results, causes for the termination of Indian Ocean dipole (IOD) events are investigated. The CGCM used here is the Scale Interaction Experiment-Frontier Research Center for Global Change (SINTEX-F1) model, which consists of a version of the European Community–Hamburg (ECHAM4.6) atmospheric model and a version of the Ocean Parallelise (OPA8.2) ocean general circulation model. This model reproduces reasonably well the present-day climatology and interannual signals of the Indian and Pacific Oceans. The main characteristics of the intraseasonal disturbances (ISDs)/oscillations are also fairly well captured by this model. However, the eastward propagation of ISDs in the model is relatively fast in the Indian Ocean and stationary in the Pacific compared to observations. A sudden reversal of equatorial zonal winds is observed, as a result of significant intraseasonal disturbances in the equatorial Indian Ocean in November–December of IOD events, which evolve independently of ENSO. A majority of these IOD events (15 out of 18) are terminated mainly because of the 20–40-day ISD activity in the equatorial zonal winds. Ocean heat budget analysis in the upper 50 m clearly shows that the initial warming after the peak of the IOD phenomenon is triggered by increased solar radiation owing to clear-sky conditions in the eastern Indian Ocean. Subsequently, the equatorial jets excited by the ISD deepen the thermocline in the southeastern equatorial Indian Ocean. This deepening of the thermocline inhibits the vertical entrainment of cool waters and therefore the IOD is terminated. IOD events that co-occur with ENSO are terminated owing to anomalous incoming solar radiation as a result of prevailing cloud-free skies. Further warming occurs seasonally through the vertical convergence of heat due to a monsoonal wind reversal along Sumatra–Java. On occasion, strong ISD activities in July–August terminated short-lived IOD events by triggering downwelling intraseasonal equatorial Kelvin waves.

scholarly journals Decadal SST Variability in the Southeast Indian Ocean and Its Impact on Regional Climate

2019 ◽  
Vol 32 (19) ◽  
pp. 6299-6318 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Lei Zhang ◽  
Fan Wang
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Indian Ocean ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Turbulent Heat ◽  
Central Pacific ◽  
Offshore Area ◽  
Sst Variability

Abstract The southeast Indian Ocean (SEIO) exhibits decadal variability in sea surface temperature (SST) with amplitudes of ~0.2–0.3 K and covaries with the central Pacific (r = −0.63 with Niño-4 index for 1975–2010). In this study, the generation mechanisms of decadal SST variability are explored using an ocean general circulation model (OGCM), and its impact on atmosphere is evaluated using an atmospheric general circulation model (AGCM). OGCM experiments reveal that Pacific forcing through the Indonesian Throughflow explains <20% of the total SST variability, and the contribution of local wind stress is also small. These wind-forced anomalies mainly occur near the Western Australian coast. The majority of SST variability is attributed to surface heat fluxes. The reduced upward turbulent heat flux (QT; latent plus sensible heat flux), owing to decreased wind speed and anomalous warm, moist air advection, is essential for the growth of warm SST anomalies (SSTAs). The warming causes reduction of low cloud cover that increases surface shortwave radiation (SWR) and further promotes the warming. However, the resultant high SST, along with the increased wind speed in the offshore area, enhances the upward QT and begins to cool the ocean. Warm SSTAs co-occur with cyclonic low-level wind anomalies in the SEIO and enhanced rainfall over Indonesia and northwest Australia. AGCM experiments suggest that although the tropical Pacific SST has strong effects on the SEIO region through atmospheric teleconnection, the cyclonic winds and increased rainfall are mainly caused by the SEIO warming through local air–sea interactions.

scholarly journals Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

2009 ◽  
Vol 22 (8) ◽  
pp. 2023-2038 ◽  
Author(s):  
Yan Du ◽  
Shang-Ping Xie ◽  
Gang Huang ◽  
Kaiming Hu
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Circulation Model ◽  
Ocean Dynamics ◽  
Northwest Pacific ◽  
Basin Scale ◽  
The Mean ◽  
Second Peak

Abstract El Niño induces a basin-wide increase in tropical Indian Ocean (TIO) sea surface temperature (SST) with a lag of one season. The north IO (NIO), in particular, displays a peculiar double-peak warming with the second peak larger in magnitude and persisting well through the summer. Motivated by recent studies suggesting the importance of the TIO warming for the Northwest Pacific and East Asian summer monsoons, the present study investigates the mechanisms for the second peak of the NIO warming using observations and general circulation models. This analysis reveals that internal air–sea interaction within the TIO is key to sustaining the TIO warming through summer. During El Niño, anticyclonic wind curl anomalies force a downwelling Rossby wave in the south TIO through Walker circulation adjustments, causing a sustained SST warming in the tropical southwest IO (SWIO) where the mean thermocline is shallow. During the spring and early summer following El Niño, this SWIO warming sustains an antisymmetric pattern of atmospheric anomalies with northeasterly (northwesterly) wind anomalies north (south) of the equator. Over the NIO as the mean winds turn into southwesterly in May, the northeasterly anomalies force the second SST peak that persists through summer by reducing the wind speed and surface evaporation. Atmospheric general circulation model experiments show that the antisymmetric atmospheric pattern is a response to the TIO warming, suggestive of their mutual interaction. Thus, ocean dynamics and Rossby waves in particular are important for the warming not only locally in SWIO but also on the basin-scale north of the equator, a result with important implications for climate predictability and prediction.

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