Observed changes in extreme temperature and precipitation over Indonesia

ABSTRACT This paper documents the changes in climate extremes over Indonesia during the past three decades (1983–2012) based on a subset of extreme indices recommended by the Expert Team on Climate Change Detection and Indices ( ETCCDI ). The extreme indices were calculated based on the quality controlled daily observational data (minimum and maximum temperature and precipitation) from 88 weather stations. Overall, we found significant and spatially coherent trends of warming in the temperature indices over Indonesia, consistent with other studies conducted at different countries within the Southeast Asia. The frequency of cool days ( TX10p ) and cools nights ( TN10p ) had decreased whereas warm days ( TX90p ) and warm nights ( TN90p ) were observed more frequently. Averaged over the country, the annual mean of daily maximum ( TXmean ) and minimum temperature ( TNmean ) had increased significantly by 0.18 and 0.30 °C decade −1 , respectively. Other temperature indices also showed significant warming trends. In contrast, trends in the precipitation extremes indices were generally not significant and less spatially coherent. However, a tendency towards wetter conditions was observed, in agreement with the results at the global scale. The daily precipitation intensity ( SDII ) had increased significantly over the country by 0.21 mm day −1 decade −1 during the period studied. At the regional scale, we observed a significant wetting trend in the annual highest daily amount ( RX1day ) and the rainfall amount contributed by the extremely very wet days (R99p) in the northern part of the country. The wetting trends of a number of extreme precipitation indices were depicted prominently in December–January–February ( DJF ) and/or March–April–May ( MAM ) seasons, both at country and regional levels. However, for the southern region of Indonesia, a drying tendency was observed for June–July–August ( JJA ), September–October–November ( SON ) and MAM .