Impact of the Madden-Julian Oscillation on Remote Ocean Variability: Low-latitude Western Boundary Current and Circulations in the Maritime Continent

During the 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 remote ocean response to these unique MJO events are investigated using satellite altimeter data and high resolution (1/25°) global ocean general circulation model; Hybrid Coordinate Ocean Model (HYCOM). The strong westerlies associated with these MJO events, which exceed 10 m/s, 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 satellite altimeter data show that anomalous sea surface height (SSH) associated with the strong eastward jets propagated eastward as an equatorial Kelvin wave. The positive SSH anomalies centered around 4S and 4N then partly propagate westward as a reflected Rossby wave. The SSH fluctuations in the southern hemisphere propagate all the way to the western boundary. These remote ocean responses are well simulated by a global HYCOM. The analysis of HYCOM simulation indicates the significant influence of reflected Rossby waves on sub-seasonal variability of Somali current system and upper ocean structure near the western boundary. The influence on remote ocean variability in the Maritime Continent and Pacific western boundary is further discussed.