Temperature, extreme precipitation, and diurnal rainfall changes in the urbanized Jakarta city during the past 130 years

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 100 mm.day-1 has shown a statistically significant increase over the 1866-2010 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 a 10-year return period is higher 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 nighttime 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.