Year of the Maritime Continent - Scientific Bases for the Campaign

While it is well recognized that the Maritime Continent (MC) plays a key role in controlling the weather and climate continuum of the entire the globe, since it occupies the upward branch of the Walker and Hadley circulations, the behaviors of many atmospheric, oceanic, and coupled phenomena over the MC are still unrevealed mysteries. For example, when the most dominant tropical intraseasonal mode known as the Madden-Julian Oscillation propagates over the MC, its signal often becomes unclear probably due to the interaction with local circulation related to the diurnal cycle and complicated topography with steep mountains surrounded by warm waters. However, their mechanism has no consensus yet. In addition, most climate models are still suffering from the large systematic errors of precipitation amount compared to the observations with overestimate/underestimate over the land/ocean. To mitigate these errors, a new field campaign called Year of the Maritime Continent or YMC is proposed. The campaign is expected to be taken place from April 2017 through October 2018, and several internationally coordinated intensive observations aiming at various research topics are planned during this one year half period. Analyses of radiosonde sounding data as well as sea surface temperature data in the MC region show the geographical preference of their time-scale variations; intraseasonal variability is dominant over the eastern MC region, while various time-scale (a few days - intraseasonal) variations in addition to diurnal cycle are found in the western MC region. Thus, observation strategy should be made by considering these features.