Convective activities over the southwestern coastal land of Sumatra island, Indonesia, during the Pre-YMC 2015 and YMC-Sumatra 2017 campaigns
Abstract
An international research project named Years of the Maritime Continent (YMC) is being implemented during 2017-2019 to expedite the progress of improving understanding and prediction of local multi-scale variability of the Maritime Continent (MC) weather-climate system and its global impact through observations and modeling exercises. We carried out two campaign observations over the southwestern coastal land and adjacent sea of Sumatra Island, Indonesia, during November-December 2015 (pre-YMC 2015: 49 days) and November 2017-January 2018 (YMC-Sumatra 2017: 61 days). We deployed two land observation sites at Bengkulu city in the southwestern coast of Sumatra Island with various kinds of instruments including automatic weather stations and an X-band polarimetric radar, and the R/V Mirai over the coastal sea of Mentawai Strait with a C-band polarimetric radar. In addition, intensive 3-hourly soundings both over the land and the vessel were conducted during the periods. Synoptic conditions during the Pre-YMC 2015 (YMC-Sumatra 2017) corresponded to El Niño (La Niña) and largescale cloud areas of active Madden-Julian Oscillation (MJO) passed over Sumatra Island in the about later (former) 10 days of the period, i.e., most of the both campaign periods were convectively MJO inactive phases. Period averaged rainfall amounts at Bengkulu site during the YMC-Sumatra 2017 was 12.4 mm/day which was approximately 25 % smaller than that during the Pre-YMC 2015 (15.9 mm/day) though the both periods corresponded to mostly MJO inactive phases. Rainfall diurnal variation in the YMC-Sumatra 2017 was quite unclear and its peak time delayed approximately 2 hours in comparison with those in the Pre-YMC 2015. In addition, although thunderstorms that lasted for several hours were observed everyday (31 days) during the Pre-YMC 2015 until MJO convections arrived over Sumatra Island, however those during the YMC-Sumatra 2017 were reported quite few (9 days) and only a short time. Characteristics which brought different convective activities between two campaign periods, e.g., diurnally developed local winds along the coastline, instabilities in the atmospheric boundary layers, and spatiotemporal variations of radar echo distribution over the coastal land, were analyzed for further discussion.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A43O3332M
- Keywords:
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- 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSESDE: 4231 Equatorial oceanography;
- OCEANOGRAPHY: GENERAL