Abstract
This study aims to explore the contrasting characteristics of large-scale circulation that led to the precipitation anomalies over the northern parts of Sumatra Island. Further, the impact of varying the Asian–Australian Monsoon (AAM) was investigated for triggering the precipitation variability over the study area. The moisture budget analysis was applied to quantify the most dominant component that induces precipitation variability during the JJA (June, July, and August) period. Then, the composite analysis and statistical approach were applied to confirm the result of the moisture budget. Using the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Anaysis Interim (ERA-Interim) from 1981 to 2016, we identified 9 (nine) dry and 6 (six) wet years based on precipitation anomalies, respectively. The dry years (wet years) anomalies over the study area were mostly supported by downward (upward) vertical velocity anomaly instead of other variables such as specific humidity, horizontal velocity, and evaporation. In the dry years (wet years), there is a strengthening (weakening) of the descent motion, which triggers a reduction (increase) of convection over the study area. The overall downward (upward) motion of westerly (easterly) winds appears to suppress (support) the convection and lead to negative (positive) precipitation anomaly in the whole region but with the largest anomaly over northern parts of Sumatra. The AAM variability proven has a significant role in the precipitation variability over the study area. A teleconnection between the AAM and other global circulations implies the precipitation variability over the northern part of Sumatra Island as a regional phenomenon. The large-scale tropical circulation is possibly related to the PWC modulation (Pacific Walker Circulation).
Highlights
Understanding of the mechanism causing precipitation variability is crucial for a comprehensive investigation of the hydrologic cycle [1]
This study focused on the statistical characteristics, and the significant correlation coefficients among three data sets suggest the usefulness of ERA-interim precipitation for a study in this data-scarce region
Note that JJA is the dry season in Sumatra Island, and the precipitation seen in Figure 2a is the lowest in the whole year
Summary
Understanding of the mechanism causing precipitation variability is crucial for a comprehensive investigation of the hydrologic cycle [1]. The study about precipitation over the tropical western Pacific and the eastern Indian Ocean is essential because the Indonesian Maritime Continent (IMC) is called the world’s convection center or the region of maximum precipitation on Earth [2,3]). Considering the vast quantities of precipitation, a thorough study focusing on the driving mechanism of precipitation variability over the Indonesian archipelago would significantly contribute to understanding the IMC’s climate system. Several studies have been done related to the precipitation variability over the Indonesian region and its relation to large-scale climatic phenomena such as Indonesian archipelago would significantly contribute to understanding the IMC2’sofc2li0-. Several studies have been done related to the precipitation variability over the Indonesian region and its relation to large-scale climatic phenomena such as El Niño–. Ts h[7e–s9c]a.rTchitey socfaorbcisteyrvoaftoiobnsedrvataatiionnodthaetar IisnlaontdhesrinIsIlnadnodnseisniaInisdroenleasteiad itsorleilmatieteddtowleimatihteerd swtaetaiothnesr, wstahtiicohnsc,anwnhoitchcocvaenrnoaltlctohveerInadllotnheesiIan’sdoisnleasnidas’s. iAsladnedtasi.leAd dsteutadiyleadbsotuutdtyheabmoeucthtahneimsmecohfapnriescmipoitfaptiroencivpaitraiatiboinlitvyawriaabsirliatryewlyacsornadreulcytecdoninduScutmedatirna SIsulmanadtr, aesIpsleacniadl,lyesipnetchiaellnyoirnthtehrennpoarrtthseornf tphaeritsslaonf dth. e island
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