Proyeksi Telekoneksi ENSO dan IOD terhadap Curah Hujan Musiman Pulau Jawa

Abstract

Variasi curah hujan musiman di Pulau Jawa dimodulasi oleh faktor pengendali variabilitas iklim seperti El Niño–Southern Oscillation (ENSO) dan Indian Ocean Dipole (IOD) melalui mekanisme telekoneksi. Studi ini mengkaji respons curah hujan musiman Pulau Jawa terhadap peristiwa ENSO dan IOD pada periode proyeksi jangka menengah (2031-2060). Luaran model Coupled Model Intercomparison Project Phase 6 (CMIP6) dianalisis menggunakan tiga skenario Shared Socioeconomic Pathways (SSP) - Representative Concentration Pathways (RCP): SSP1-2.6, SSP2-4.5, dan SSP5-8.5. Fase ENSO dan IOD diidentifikasi dengan Oceanic Niño Index (ONI) dan Dipole Mode Index (DMI) serta proses koreksi bias diterapkan untuk mereduksi keterbatasan model. Hubungan antara curah hujan dan setiap indeks diukur menggunakan regresi linear untuk menguji kekuatan telekoneksi dan variasi spasial. Hasilnya menunjukkan respons curah hujan musiman terhadap ENSO menguat ke arah negatif, khususnya selama musim JJA-SON dengan slope -3,5 mm/hari/°C. Adapun proyeksi respons curah hujan terhadap IOD menunjukkan kecenderungan slope negatif, walaupun polanya tidak konsisten di semua skenario. Pengaruh IOD+ diproyeksikan tetap dominan pada JJA–SON dengan rata-rata slope mencapai –2,0 mm/hari/°C. Proyeksi ini mengindikasikan potensi kekeringan ekstrem di Pulau Jawa akibat intensifikasi peristiwa fase hangat ENSO dan IOD serta respons penurunan curah hujan yang lebih kuat di musim kemarau.

Seasonal rainfall variability in Java Island is modulated by climate variability drivers, such as the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) through teleconnection mechanisms. This study aims to assess the projected response of Java’s seasonal rainfall to ENSO and IOD events in the near future period (2031–2060). Outputs from Coupled Model Intercomparison Project Phase 6 (CMIP6) models were analyzed under three Shared Socioeconomic Pathways (SSP) - Representative Concentration Pathways (RCP) scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. ENSO and IOD phases were identified using the Oceanic Niño Index (ONI) and Dipole Mode Index (DMI) and a bias correction process was applied to reduce model limitations. The relationship between seasonal rainfall and each index was quantified using linear regression to examine teleconnection strength and spatial variation. The results show that the seasonal rainfall variability associated with ENSO becomes increasingly negative, particularly during the JJA-SON season, with a slope of -3.5 mm/day/°C. Meanwhile, the projected rainfall response to the IOD shows a tendency toward a negative slope, although the pattern remains inconsistent across scenarios. The influence of IOD+ is projected to remain dominant during JJA–SON, with an average slope reaching –2.0 mm/day/°C. These projections indicate a potential for more extreme drought conditions in Java due to the intensification of warm-phase ENSO and IOD events, alongside a stronger reduction in rainfall during the dry season.