Influence of ENSO on the Diurnal Cycle of Rainfall over the Maritime Continent and Australia

Abstract

This study examines the influence of ENSO on the diurnal cycle of rainfall during boreal winter for the period 1998–2010 over the Maritime Continent (MC) and Australia using Tropical Rainfall Measuring Mission (TRMM) and reanalysis data. The diurnal cycles are composited for the ENSO cold (La Niña) and warm (El Niño) phases. The k-means clustering technique is then applied to group the TRMM data into six clusters, each with a distinct diurnal cycle. Despite the alternating patterns of widespread large-scale subsidence and ascent associated with the Walker circulation, which dominates the climate over the MC during the opposing phases of ENSO, many of the islands of the MC show localized differences in rainfall anomalies that depend on the local geography and orography. While ocean regions mostly experience positive rainfall anomalies during La Niña, some local regions over the islands have more rainfall during El Niño. These local features are also associated with anomalies in the amplitude and characteristics of the diurnal cycle in these regions. These differences are also well depicted in large-scale dynamical fields derived from the interim ECMWF Re-Analysis (ERA-Interim).

How important is tropospheric humidity for coastal rainfall in the tropics?

“…Using an objective pattern recognition technique Bergemann et al [] showed that in coastal regions of the tropics, in particular over the many islands of the Maritime Continent, coastally influenced rainfall constitutes more than a third of the overall annual rainfall received, indicating its importance for the region and its likely strong effect on the large‐scale circulation through convective heating effects [ Neale and Slingo , ]. Several recent studies [ Rauniyar and Walsh , , ; Peatman et al , ; Bergemann et al , ] have presented evidence that the rainfall characteristics of large‐scale tropical circulations, such as the Madden‐Julian Oscillation (MJO) [ Madden and Julian , , , ], are strongly modified by the presence of coasts. They showed that in the coastal regions of the Maritime Continent, rainfall is strongly modulated by coastline effects leading to enhanced precipitation in the suppressed MJO phase and therefore very small differences in rainfall between active and suppressed MJO conditions over the land regions of the Maritime Continent.…”

Diverse impacts of ENSO on wintertime rainfall over the Maritime Continent

“…Previous studies indicated that the tropical Pacific sea surface temperature (SST) is one of the important factors influencing the variability of precipitation over the Maritime Continent (Lau and Chang, 1987;Wang et al, 2000Wang et al, , 2003Wu et al, 2003;Chang et al, 2004;Feng et al, 2010;Qian et al, 2010;Wang and Chen, 2010;Chen et al, 2013aChen et al, , 2013bRauniyar and Walsh, 2013;Smith et al, 2013). The processes through which the tropical Pacific SST influences climate variation over the Maritime Continent (Zhang et al, 1996;Chang et al, 2000;Wang et al, 2000;Feng et al, 2010;Wu et al, 2010) and the East Asian region (e.g.…”

The Holocene environmental changes in southern Indonesia reconstructed from highland caldera lake sediment in Bali Island

“…This trend is different from our data of dry mid Holocene and wet late Holocene in spite of regional proximity. However, their vegetation reconstruction represented mainly those of low altitude plain in nearby Island, and recent modeling study (Qian et al, 2010) and meteorological data (Rauniyar and Walsh, 2013) in Indonesian islands observed large decrease of wet season rainfall in El Niño years in low altitude plains or oceanic area, whereas it increased in mountainous area due to local changes of wind directions and orographic convergence effect on atmospheric circulation. In view of this, local altitudinal difference could be the cause of the opposite rainfall trends.…”

“…Terrestrial lacustrine deposits have potential to show more immediate data of rainfall variations that are most concerned issues for socioeconomics, but more numbers of sedimentary records are necessary as they are often discontinuous due to frequent episodic sedimentation events (Pirrung et al, 2004(Pirrung et al, , 2005Rodysill et al, 2012). Terrestrial archives could be also influenced by local climate features related to configuration of islands and regional topography (Rauniyar and Walsh, 2013;Dubois et al, 2014).…”