PREDIKTIBILITAS CURAH HUJAN DIURNAL DI PULAU JAWA MENGGUNAKAN MODEL WRF [PREDICTIBILITY OF DIURNAL RAINFALL OVER JAVA ISLAND USING WRF]
Abstract
Indonesian region often experiences hydrometeorological disasters such as floods and landslides. To mitigate the losses from such disasters, an early warning system is needed. PSTA LAPAN has developed an early warning system called SADEWA (Satellite Disaster Early Warning System). The performance of this early warning system needs to be evaluated in order to increase the confidence level. The evaluation of the WRF performance in producing the prediction was carried out by analyzing the diurnal cycles of rainfall over Java and its surroundings using the results of WRF predictions implemented in SADEWA and GSMaP data for one year period (Maret 2014 – Februari 2015). The contrasting diurnal cycles between Java island and its surrounding seas could be well simulated by the WRF model, both the amount and the frequency of the rainfall. However, the phase of diurnal cycle from the WRF prediction leads that of the observation by two hours and the amplitude of the simulated diurnal cycle is higher than the observed. The results also show that the WRF predictions could not simulate the effects of MJO (Madden-Julian Oscillation) on the diurnal cycles of rainfall over Java.
ABSTRAK
Wilayah Indonesia sering mengalami bencana hidrometeorologi seperti banjir dan tanah longsor. Untuk mengurangi kerugian yang diakibatkan oleh kejadian bencana meteorologi diperlukan suatu sistem peringatan dini. PSTA LAPAN telah mengembangkan sebuah sistem peringatan dini yang diberi nama SADEWA (Satellite Disaster Early Warning System). Kinerja sistem peringatan dini seperti ini perlu dievaluasi agar tingkat kepercayaannya meningkat. Evaluasi kinerja hasil prediksi ini dilakukan dengan menganalisis siklus diurnal curah hujan di pulau Jawa dan sekitarnya pada data hasil prediksi WRF yang digunakan dalam SADEWA dan data GSMaP selama satu tahun (Maret 2014 – Februari 2015). Siklus diurnal curah hujan yang kontras antara pulau Jawa dengan lautan sekitarnya mampu disimulasikan dengan baik oleh model WRF, baik dari jumlah maupun frekuensi curah hujannya. Namun fasa diurnal dari hasil prediksi WRF mendahului fasa data pengamatan sekitar dua jam dan mempunyai amplitudo lebih besar. Hasil analisis juga menunjukkan hasil prediksi WRF belum mampu mensimulasikan pengaruh MJO (Madden-Julian Oscillation) pada siklus diurnal curah hujan di Jawa.
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