The Dependence of Indonesia's Precipitation Response to Anthropogenic Aerosols on Emission Location

Precipitation is a significant source of fresh water that supports life in countless ways. Societies depend on the patterns and amounts of precipitation that they are accustomed to and anything that threatens to alter the hydrological cycle will have serious socio-environmental implications. Anthropogenic aerosols can strongly influence regional precipitation by modifying the atmospheric thermodynamics, dynamical circulation patterns, and microphysical cloud processes that produce it. For instance, aerosols can shift the Intertropical Convergence Zone, responsible for most of the precipitation in the tropics, by generating asymmetrical temperatures between the hemispheres as the ITCZ will shift towards the warmer hemisphere. This research focuses on Indonesian precipitation and how it is affected by aerosols from local and remote areas. Indonesia, a country composed of multiple islands, is a compelling region to study as it has the fourth largest population with approximately 270 million people and is newly industrialized. It is in the tropics situated on the equator, so its precipitation is predominantly governed by the movement of the Intertropical Convergence Zone (ITCZ). Using the Community Earth System Model, we test how Indonesian precipitation responds to identical aerosols emitted from Indonesia versus 7 other key regions. We find that aerosol emissions from 7 of the 8 total regions suppress Indonesia’s precipitation with Indonesia having the largest impact followed by the United States then India. In the case of the United States, an example of remote aerosol influence, aerosols appear to impact Indonesian precipitation primarily by shifting the ITCZ. Notably, China was the only country where aerosols were placed that increased Indonesian precipitation. We further investigate the influence that the various aerosol source regions have on the seasonal cycle of Indonesian precipitation and place those effects in the context of Indonesia’s society and economy.