Rainfall variability in the Austral-Indonesian Region and the role of Indo-Pacific climate drivers

Abstract

The tropical Austral-Indonesian region (95°E-155°E, 25°S-10°N) is a strategically important region in the climate system and is sensitive to extreme events caused by climate variability and change. Its unique position induces significant consequences in global and regional climate distributions and is challenging for climate model studies. Rainfall is one of the economically most significant climate variables in the region and is sensitive to regional and large-scale climate events on various timescales. The present study delivers a comprehensive assessment and analysis of rainfall variability and its link with Indo-Pacific climate drivers such as the El Niño-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the low-frequency modulation of the Interdecadal Pacific Oscillation (IPO). It involves some analyses of observational datasets as well as analyses of global climate model (GCM) outputs. Firstly, the study presents an assessment of historical and future rainfall simulated by twenty-one climate models that contributed to the Intergovernmental Panel on Climate Change Fourth Assessment Report. It then evaluates the basic features of seasonal rainfall climatology as well as their variability and trends. The results determine the three best-performing models for rainfall simulations in the region. Secondly, leaning on the observed data, the study investigates seasonal patterns of regional sea surface temperature and rainfall and their associations with Indo-Pacific climate drivers on interannual and interdecadal timescales. The results show the significant role of regional sea surface temperature in regulating the effect of Indo-Pacific climate drivers on rainfall variability in the region as well as in moderating the ENSO-IOD dependency. Thirdly, more specific analysis aims to identify the physical processes of the leading rainfall patterns relied on climate model output in pre-industrial control run simulations. The analysis finds that the independency of IOD from ENSO is more regulated by the regional SST condition in the Austral-Indonesian region.