Dampak Asimilasi Data Radar Produk Cappi pada Prediksi Kejadian Hujan Lebat di Jabodetabek Menggunakan Model WRF-3DVAR
DOI:
https://doi.org/10.31172/jmg.v20i1.605Keywords:
asimilasi radar, model cuaca, radar, CAPPI, JabodetabekAbstract
Penelitian ini dilakukan untuk mengevaluasi dampak asimilasi data radar pada model WRF untuk prediksi kejadian hujan ekstrim di wilayah Jabodetabek pada tanggal 11 Desember 2017 yang disebabkan oleh angin monsun barat serta adanya konvergensi dan shearline di wilayah utara Pulau Jawa. Dua eksperimen model WRF dengan data inisial Global Forecast System (GFS) pukul 00.00 UTC dilakukan untuk memprediksi 24 jam ke depan, yaitu (1) tanpa asimilasi data dan (2) dengan asimilasi data reflektifitas radar cuaca dengan teknik 3DVAR. Analisis dilakukan dengan membandingkan parameter mixing ratio dan curah hujan dari data inisial kedua eksperimen. Uji skill dan keandalan model dalam prediksi curah hujan dilakukan dengan verifikasi luaran model pada 5 stasiun pengamatan di Bandara Sekarno-Hatta (Soetta), Pondok Betung (Ponbet), Kemayoran, Tanjung Priok dan Citeko menggunakan teknik dikotomi (penggolongan hujan/tidak hujan). Hasil menunjukan bahwa data reflektifitas radar (Z) berdampak pada perubahan nilai prediksi parameter mixing ratio yang berpengaruh terhadap pertumbuhan awan di wilayah Jabodetabek. Analisis skill Percent Correct (PC), Probabilty of Detection (POD) dan False Alarm Ratio (FAR) menunjukan adanya perbaikan pada eksperimen model dengan asimilasi data radar 3DVAR. Selain itu, analisis skill pada stasiun pengamatan Soekarno-Hatta selalu menunjukan nilai terbaik dibandingkan dengan stasiun pengamatan lainnya yang berjarak lebih jauh dari radar cuaca. Penelitian ini dengan jelas menyarankan bahwa asimilasi data (3DVAR) memiliki dampak positif dan perbaikan prakiraan pada simulasi kejadian hujan ekstrim.References
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