Analisis Dampak Gelombang Equatorial Rossby terhadap Kejadian Cuaca Ekstrem di Wilayah Indonesia
Keywords:
Gelombang Equatorial Rossby, dinamika atmosfer, musim hujan, probabilitas hujan ekstrem, IndonesiaAbstract
Gelombang Equatorial Rossby (ER) merupakan gelombang ekuatorial yang memiliki struktur gyre atau twin vortices di belahan bumi utara (BBU) dan belahan bumi Selatan (BBS) saat melintas di wilayah ekuator. Twin vortices tersebut mampu memengaruhi pergerakan massa udara dan memodulasi terbentuknya cuaca ekstrem. Penelitian ini bertujuan untuk menganalisis pola klimatologis dinamika atmosfer pada hari aktif gelombang ER di musim hujan (Desember, Januari, Februari) dan menganalisis wilayah yang berpotensi mengalami peningkatan kejadian cuaca ekstrem pada periode kajian. Data yang digunakan yakni data reanalisis ERA5 meliputi geopotential, angin u dan v, dan kelembapan spesifik(q), anomali outgoing longwave radiation (OLR) CPC NOAA, dan curah hujan PERSIANN-CDR. Pengolahan data dilakukan dengan metode filter Space Time Spectral Analysis (STSA), Empirical Orthogonal Function (EOF) dan analisis komposit hari aktif ER (indeks fase ER). Hasil penelitian menunjukkan bahwa aktivitas gelombang ER mengakibatkan ketidakstabilan atmosfer sehingga memicu terbentuknya awan konvektif dan meningkatkan probabilitas kejadian hujan ekstrem. Pada fase aktif, pusaran siklonik memicu konvergensi masif dan memodulasi pembentukan awan konvektif pada fase 7, 8, 1 dan 2 di sebagian besar wilayah Indonesia. Sebaliknya, pada fase 3, 4, 5 dan 6, pusaran antisiklonik mendukung terjadinya supresi konvektif yang menyebabkan divergensi dan menekan terbentuknya awan konvektif di wilayah Indonesia bagian timur dan tengah. Meskipun demikian, wilayah barat Indonesia tetap mengalami anomali konvergensi, akibat pengaruh topografi dan aliran massa udara dari Samudera Hindia. Informasi wilayah yang berpotensi terjadi hujan ekstrem dapat digunakan dalam upaya mitigasi dan peringatan dini cuaca ekstrem saat gelombang ER terpantau aktif. Oleh karena itu, pada penelitian selanjutnya dibutuhkan analisis lebih lanjut mengenai superposisi gelombang ER dengan sistem monsun maupun anomali iklim global lainnya.
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