Interannual Rainfall Variability over the Eastern Maritime Continent

Abstract

The authors investigate the interannual rainfall variability over the eastern maritime continent using station rainfall data in the Republic of Palau during 1923 and Eastern Indonesia during 1973-2008. Two possible mechanisms are proposed to explain the interannual rainfall variability associated with the El Niñ o/Southern Oscillation over the surrounding region of the Banda and Arafura seas.During the El Niñ o developing year, rainfall starts to decrease, first in region close to the equator in summer than in o¤-equatorial region in autumn, such as in mainland Palau. Eastern Indonesia has a dry season during boreal summer in general, and the dry season becomes a significantly drier condition during El Niñ o years. The start of increasing rainfall is delayed. Cloud data show a convection-suppressed region from the east coast of the Kalimantan to the west coast of the New Guinea during July to November of El Niñ o years.One of the mechanisms for these changes is the air-sea interaction over the Banda and Arafura seas. Intensification of seasonal southerly wind associated with the western North Pacific monsoon decreases sea-surface temperature over the Banda and Arafura seas, and convection is more suppressed during El Niñ o years than other years. Another mechanism is the subsidence over the Banda and Arafura seas during the pre-monsoon of the Australian summer monsoon. Land-ocean thermal contrast between Australia and its surrounding seas is intensified during El Niñ o years. Shallow thermal convection produces subsidence over the Banda and Arafura seas, and extremely dry condition spreads over the surrounding region in October during El Niñ o years.

Maritime continent coastlines controlling Earth’s climate

“…More detailed correlation analyses of recent improved rainfall observations for West Jawa with SST over the Central Pacific and Western Indian Oceans ) and for the eastern IMC (Kubota et al 2011;Lestari et al 2016) are now being applied to the whole of Indonesia. SST variations may reduce or amplify the nighttime sea-to-land temperature gradient and control the morning coastal-sea rainfall in particular in the dry season.…”

“…In particular, west−east differences of the IMC have been found in climatological (e.g., Köppen 1918;Murakami and Matsumoto 1994;Kubota et al 2011;Hidayat et al 2016;Lestari et al 2016), and cloudphysical (e.g., As-syakur et al 2016) and water isotope (Suwarman et al 2013(Suwarman et al , 2017Belgaman et al 2016;Permana et al 2016) observations. The western part has relatively greater rainfall, a more continental-like raindrop size distribution, and more Indian Ocean monsoon-like origin than the eastern part.…”

“…The interannual variations of rainfall over the IMC and their relation with ENSO and IOD have been analyzed in several studies (e.g., Hamada et al 2002Hamada et al , 2008Hamada et al , 2012Aldrian and Susanto 2003;Kubota et al 2011;Siswanto et al 2016;Yanto et al 2016;Lestari et al 2016;As-syakur et al 2016) (Fig. 15).…”

ENSO Influences on Rainfall Extremes around Sulawesi and Maluku Islands in the Eastern Indonesian Maritime Continent

“…This implies that the eastern IMC may be more sensitive region for droughts by increasing number of consecutive dry days. Interannual rainfall variability in the IMC has strong relationship with El Niño Southern Oscillation (ENSO) (Hamada et al 2002Hendon 2003;Kubota et al 2011). Rainfall tends to increase during La Niña years, especially in the eastern part of the IMC during boreal summer and autumn than in winter (Chang et al 2004).…”

Intraseasonal Variability of δ¹⁸O of Precipitation over the Indonesian Maritime Continent Related to the Madden–Julian Oscillation

“…Op and TPW during the MJO event suggested that seasonal and interannual variability possibly have more dominant effects because of the geographic position and topographic condition (e.g., Kubota et al 2005Kubota et al , 2011.…”