Change in the Indonesian Seas with the circulation and heat and freshwater inventories and associated air-sea fluxes of the regional and global oceans. This white paper puts forward the design of an observational array using multi-platforms combined with high-resolution models aimed at increasing our quantitative understanding of water mass transformation rates and advection within the Indonesian seas and their impacts on the air-sea climate system.

Using a newly available 134-years long record of daily and 114-years hourly observations at Jakarta observatory, trends and variability in temperature, extreme precipitation, and changes in the diurnal cycle over Jakarta have been analysed. Although the number of days with rainfall has decreased over the 1866-2010 period, the fraction of events with rainfall exceeding 50 mm day −1 exhibits a positive trend over the 1866-2010 period with an even stronger trend over the period 1961-2010. The number of days with rainfall exceeding 50 and 100 mm day −1 has shown a statistically significant increase over the 1961-2010 period as well. Over the recent decades, the heaviest 1% of all precipitation events (q99%) also exhibits an increasing trend. These trends in extremes are strongest during the wet season. The rainfall intensity with 200 mm return level has a shorter return period in the most recent decade than earlier in the historic time series. Over the last century, the annual mean temperature in Jakarta has increased about 1.6 ∘ C per century, which exceeds the rise of the global mean land temperature. The increase in the daily maximum temperature is stronger than the increase in mean and minimum temperature, although the trend in minimum temperature is stronger during the last 50 years. The mean diurnal cycles of Jakarta temperature and precipitation have changed markedly as well. This analysis was enabled by the availability of high quality hourly observations in the historic record. Comparing the 2001-2010 period to historic decades, a considerable increase in night-time temperature was found. During the wet season, the early morning rainfall has increased in intensity, while in other seasons a delay of the late afternoon rainfall peak was observed for the recent observation periods.

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The influence of monsoonal wind to coastal upwelling mechanism which is generated by Ekman transport was studied here by analyzing wind stress curl (WSC) distribution over Java-Bali Sea waters and its surrounding area. Surface wind data were used as input data to calculate curl of wind stress in barotropic model. Confirmation with Corioli effect in the Southern Hemisphere, it could be known that negative curl value has relation with vertical motion of sea water as resulted by Ekman transport. Result of analysis showed that negative curl near coast over Java Sea which is stretching to Lombok Sea occurred in December to April when westerly wind of the North West Monsoon actives. It can be guidance and related with season of coastal upwelling in the region. Reversal condition, the occurrance of coastal upwelling in the south coast of JAva island related with the negative value of WSC that occurs since easterlies wind take place in May to August as a part of South East Monsoon episode. Generally, upwelling occurrance in the field of study is a response to the Monsoon circulation. This study with related data such as sea surface temperature, chlorophyll concetration and mixed layer depth that derived from satellite imaging data National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR), Aqua/Modis and sea viewing Wide Field-of-view Sensor(Sea WiFS) shows as magnificent confirmation pattern. So applying WSC to recoqnize upwelling zone is alternatively way as climatic approach to maps potential fertilizing of sea water in maritime-continent Indonesia. Key words: coastal upwelling, Ekman transport, Java-Bali Sea, Monsoon circulation, upwelling.

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