No abstract

Peat fire is one of the environmental disasters occurring widespread during the dry season in South Sumatra. The region has long been recognized to have extensive peatland, hence it is considered as the vulnerable areas to fire. This study employs spatial analysis to evaluate the likely linked factors causing peat fire in the study area. Two interannual climate modes such as the El Niño – Southern Oscillation and Indian Ocean Dipole were considered to have affected the area with respect to climate anomaly at the 1995-2016 periods. This phenomenon was followed by the peat fire in many areas. There appears a close linkage between the occurrence of peat fires and climate anomaly. A number of hotspots tend to occur annually during the drought season. A significant number of hotspots took place during the 2006 pIOD and 2015 El Niño events due to a significant decrease in rainfall intensities.

The respective influences of the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) on Indonesian precipitation were evaluated using monthly precipitation data from the Global Precipitation Climatology Centre (GPCC) for January 1948 to December 2013. Simultaneous correlation between seasonal precipitation anomalies and climate indices for these two types of climate modes revealed that IOD events have a significant correlation with the precipitation over southern Sumatra, Java, southern Kalimantan, the Nusa Tenggara Islands, some parts of Sulawesi and eastern Papua. Meanwhile, ENSO events have a significant correlation with the precipitation over southern Sumatra, Java, Kalimantan, Sulawesi, and Papua. Droughts during the dry season (JJA and SON) typically occur when a positive IOD event simultaneously occurs with an El Niño event associated with anomalous low SST observed in the Indonesian seas and the southeastern equatorial Indian Ocean. Low SST anomalies lead to low-level wind divergence and reduce water vapor in the lower atmosphere, supress atmospheric convection over the Indonesian region and then cause a decrease in precipitation.

No abstract

The Indonesian sea is the only low-latitude pathway connecting two tropical oceans, which plays an important role in the coupled ocean-atmosphere mode in the Indo-Pacific sector. A small change in the sea surface temperature (SST) in the Indonesian sea has a significant influence on the precipitation and air-sea heat flux. During the past 33 years, the SST in the Indonesian sea has indicated a warming trend on the average of 0.19 ± 0.04 decade−1, which is larger than global SST warming trend. Moreover, the warming trend indicates seasonal variations, in which maximum trend occurred during boreal summer season. Investigation on the potential driver for this warming trend, namely, the net surface heat flux, resulted in an opposite trend (cooling trend), while the Ekman pumping and the wind mixing only play a minor role on the SST warming. Here, we proposed the upper layer process associated with an increasing trend in precipitation and decreasing trend in mixed layer depth (MLD) for the SST warming within the Indonesian seas. Shoaling of MLD gives a favorable condition for the surface heat flux to warm the surface ocean. However, shoaling of MLD could not solely explain the total SST warming within the Indonesian seas. The seasonal dependence in the warming trend, highest during boreal summer, was significantly related to the Indo-Pacific climate modes, namely the negative Indian Ocean Dipole (IOD) and La Niña events. Higher warming trend observed in the south of Makassar Strait and in the eastern Indonesian seas, in the vicinity of the Maluku Sea and the northeastern part of the Banda Sea, was significantly associated with the La Niña event. Meanwhile, strong warming trend observed in the Karimata Strait and Java Sea, and in the Flores Sea south of Sulawesi Island seems to be enhanced by the negative IOD event. Our rough quantitative estimate of the possible mechanism leading to the SST warming suggests that other mechanism might be at work in warming the SST within the Indonesian seas. Horizontal heat advection associated with an increasing trend of the heat transport from the Pacific into the Indian Ocean by the Indonesian Throughflow (ITF) might play a role in causing the warming trend within the Indonesian seas. However, to what extend this heat advection could modulate the SST warming is still unresolved in the present study. Further study based on realistic model output as well as long-term observational records is necessary to describe the dynamics underlying the warming trend within the Indonesian seas.