scholarly journals Remote Ocean Response to the Madden–Julian Oscillation during the DYNAMO Field Campaign: Impact on Somali Current System and the Seychelles–Chagos Thermocline Ridge

Atmosphere ◽  
2017 ◽  
Vol 8 (12) ◽  
pp. 171 ◽  
Author(s):  
Toshiaki Shinoda ◽  
Weiqing Han ◽  
Luis Zamudio ◽  
Ren-Chieh Lien ◽  
Masaki Katsumata
Keyword(s):  
Current System ◽  
Madden Julian Oscillation ◽  
Field Campaign ◽  
Ocean Response ◽  
Somali Current

scholarly journals Impact of the Madden–Julian Oscillation on the Indonesian Throughflow in the Makassar Strait during the CINDY/DYNAMO Field Campaign

2016 ◽  
Vol 29 (17) ◽  
pp. 6085-6108 ◽  
Author(s):  
Toshiaki Shinoda ◽  
Weiqing Han ◽  
Tommy G. Jensen ◽  
Luis Zamudio ◽  
E. Joseph Metzger ◽  
...  
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Circulation Model ◽  
Global Ocean ◽  
Indonesian Throughflow ◽  
Madden Julian Oscillation ◽  
Field Campaign ◽  
Eastern Boundary ◽  
The Indian Ocean ◽  
Velocity Anomalies

Abstract Previous studies indicate that equatorial zonal winds in the Indian Ocean can significantly influence the Indonesian Throughflow (ITF). During the Cooperative Indian Ocean Experiment on Intraseasonal Variability (CINDY)/Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign, two strong MJO events were observed within a month without a clear suppressed phase between them, and these events generated exceptionally strong ocean responses. Strong eastward currents along the equator in the Indian Ocean lasted more than one month from late November 2011 to early January 2012. The influence of these unique MJO events during the field campaign on ITF variability is investigated using a high-resolution (1/25°) global ocean general circulation model, the Hybrid Coordinate Ocean Model (HYCOM). The strong westerlies associated with these MJO events, which exceed 10 m s−1, generate strong equatorial eastward jets and downwelling near the eastern boundary. The equatorial jets are realistically simulated by the global HYCOM based on the comparison with the data collected during the field campaign. The analysis demonstrates that sea surface height (SSH) and alongshore velocity anomalies at the eastern boundary propagate along the coast of Sumatra and Java as coastal Kelvin waves, significantly reducing the ITF transport at the Makassar Strait during January–early February. The alongshore velocity anomalies associated with the Kelvin wave significantly leads SSH anomalies. The magnitude of the anomalous currents at the Makassar Strait is exceptionally large because of the unique feature of the MJO events, and thus the typical seasonal cycle of ITF could be significantly altered by strong MJO events such as those observed during the CINDY/DYNAMO field campaign.

scholarly journals Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months

2012 ◽  
Vol 25 (8) ◽  
pp. 2824-2842 ◽  
Author(s):  
Benjamin G. M. Webber ◽  
David P. Stevens ◽  
Adrian J. Matthews ◽  
Karen J. Heywood
Keyword(s):  
Indian Ocean ◽  
Rossby Waves ◽  
Surface Wind ◽  
Wind Forcing ◽  
Global Ocean ◽  
Dynamical Response ◽  
Madden Julian Oscillation ◽  
Easterly Wind ◽  
Ocean Response ◽  
Equatorial Rossby Waves

Abstract The authors show that a simple three-dimensional ocean model linearized about a resting basic state can accurately simulate the dynamical ocean response to wind forcing by the Madden–Julian oscillation (MJO). This includes the propagation of equatorial waves in the Indian Ocean, from the generation of oceanic equatorial Kelvin waves to the arrival of downwelling oceanic equatorial Rossby waves in the western Indian Ocean, where they have been shown to trigger MJO convective activity. Simulations with idealized wind forcing suggest that the latitudinal width of this forcing plays a crucial role in determining the potential for such feedbacks. Forcing the model with composite MJO winds accurately captures the global ocean response, demonstrating that the observed ocean dynamical response to the MJO can be interpreted as a linear response to surface wind forcing. The model is then applied to study “primary” Madden–Julian events, which are not immediately preceded by any MJO activity or by any apparent atmospheric triggers, but have been shown to coincide with the arrival of downwelling oceanic equatorial Rossby waves. Case study simulations show how this oceanic equatorial Rossby wave activity is partly forced by reflection of an oceanic equatorial Kelvin wave triggered by a westerly wind burst 140 days previously, and partly directly forced by easterly wind stress anomalies around 40 days prior to the event. This suggests predictability for primary Madden–Julian events on times scales of up to five months, following the reemergence of oceanic anomalies forced by winds almost half a year earlier.

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