Electronic Theses and Dissertation

Boreal Summer Intraseasonal Oscillation (BSISO) merupakan salah satu
variabilitas iklim intramusiman atau intraseasonal oscillation (ISO) selain MaddenJulian

Oscillation (MJO) yang mempengaruhi cuaca dan iklim di kawasan IndoPasifik.

Studi BSISO terdahulu menyebutkan adanya pengaruh BSISO terhadap
variasi dan kejadian curah hujan ekstrem di wilayah Indonesia, Pulau Sumatera, dan
Provinsi Sumatera Utara selama periode musim kemarau (Mei-Oktober). Namun,
belum ditemukan penelitian terkait BSISO yang terfokus di provinsi Aceh. Sehingga
perlu memahami pengaruh BSISO terhadap variasi dan kejadian curah hujan ekstrem
di Provinsi Aceh. Penelitian ini dilakukan untuk menginvestigasi pengaruh BSISO
terhadap variasi dan kondisi curah hujan ekstrem menggunakan data curah hujan
observasi dari 5 Stasiun Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) di
Provinsi Aceh dan indeks BSISO yang terbagi menjadi BSISO1 dan BSISO2 digunakan
untuk memonitoring aktivitas BSISO selama periode Mei-Oktober tahun 2001-2020.
Hasil analisis spektral curah hujan di Aceh menunjukkan puncak energi spektral 180
harian yang berkorelasi dengan osilasi Intertropical Convergence Zone (ITCZ), dan
puncak energi spektral 40-50, memiliki kesamaan periode osilasi dengan BSISO1.
Secara umum, analisis komposit curah hujan selama BSISO1 dan BSISO2
mempengaruhi peningkatan variasi dan peluang perubahan curah hujan ekstrem di
Provinsi Aceh hingga 100% dengan peningkatan curah hujan mencapai 8 mm/hari
selama fase 1-3, dan selama fase 4-8, menunjukkan kecenderungan penurunan
peluang perubahan curah hujan ekstrem mencapai 80% dengan variasi curah hujan
menurun sebesar 6 mm/hari. Variabiltas BSISO1 juga berdampak terhadap
peningkatan peluang banjir selama fase 1-2 mencapai 90%, dan selama BSISO2
terjadi pada fase 1-3 mencapai 72%.

Kata kunci : BSISO, curah hujan ekstrem, banjir, periodogram, Aceh

The Boreal Summer Intraseasonal Oscillation (BSISO) is an intraseasonal climate variability (ISO) in addition to the Madden-Julian Oscillation (MJO) that affects weather and climate in the Indo-Pacific region. Previous BSISO studies have suggested the influence of BSISO on variations and extreme rainfall events in Indonesia, Sumatra Island, and North Sumatra Province during the dry season (May– October). However, there needs to be research related to BSISO that focuses on Aceh province. So it is necessary to understand the influence of BSISO on the variation and occurrence of extreme rainfall in Aceh Province. This study was conducted to investigate the influence of BSISO on variations and extreme rainfall conditions using observed rainfall data from 5 Meteorological, Climatological, and Geophysical Agency (BMKG) stations in Aceh Province and the BSISO index, which is divided into BSISO1 and BSISO2, used to monitor BSISO activity during the May–October period 2001–2020. The results of spectral analysis of rainfall in Aceh show that the 180 daily spectral energy peak correlates with the Intertropical Convergence Zone (ITCZ) oscillation, and the 40–50 spectral energy peak has a similar oscillation period with BSISO1. In general, the composite analysis of BSISO1 and BSISO2 influenced the increase in variation and the change of extreme rainfall probabilities in Aceh Province up to 100%, with an increase in rainfall reaching 8 mm/day during phases 1-3 and phases 4–8, showing a downward trend in the change of extreme rainfall probabilities reaching 80% with rainfall variation decreasing by 6 mm/day. BSISO1 variability also impacted the increasing change of flood probability during phases 1-2 up to 90% and BSISO2 in phases 1-3 reaching 72%.. Keywords: BSISO, extreme rainfall, flood, periodogram, Aceh