No abstract

This paper presents an overview of the HARIMAU2010 campaign focusing on convective activity with the diurnal rainfall meridional march (DRMM) over Jakarta, which is located on the northern coast of Jawa Island of the Indonesian maritime continent (IMC), based on 1-month intensive observations by a C-band Doppler radar and multi-point atmospheric sounding array conducted during 16 January-14 February 2010. The campaign period corresponded to a phase after large-scale Madden-Julian oscillation (MJO) active convections passed over Jakarta (MJO inactive phase). The cross-equatorial northerly surge (CENS) intruded into the Jawa Sea with a cold tongue (CT) of sea surface temperature (SST) in the beginning of the period (CENS active period: 16-26 January), and then, it started to retreat (transition period: 27 January-05 February); afterward, only a few signs of it were apparent (CENS inactive period: 06-14 February). The observational results showed that (1) rainfall over Jakarta has the nature of DRMM during the MJO inactive phase at least, (2) the DRMM is likely driven primarily by "land-breeze"-like local meridional circulation, and (3) the meridional spatiotemporal variation of rainfall over Jakarta is thus controlled by activities of both the CENS and CT over the Jawa Sea.

No abstract

El Niño Southern Oscillation (ENSO) influences on rainfall extremes around Sulawesi and the Maluku Islands in the eastern Indonesian Maritime Continent were investigated focusing on spatial and seasonal aspects using daily rainfall data at 23 stations during 1972−2012. The results show that interannual variations in rainfall extremes were strongly correlated with the ENSO phases. Wetter (drier) conditions were associated with La Niña (El Niño) events, in terms of total precipitation, rainy days, and consecutive dry days at more than 90% of the stations. Dry days tend to increase more than 2 months in the El Niño than La Niña years causing severe droughts in the region. Frequency and number of stations of heavy rainfalls increased (decreased) during La Niña (El Niño) events, whereas ENSO influences were weak (strong) on severest (moderately intense) rainfall events. ENSO influences on rainfall amount and number of rainy days vary spatially and seasonally. They were predominant during July-November but less during December-February. Heavy rainfall frequency was significantly higher during La Niña than El Niño years in transitional seasons.