Akurasi prakiraan curah hujan harian operasional yang dibuat oleh Badan Meteorologi Klimatologi dan Geofisika (BMKG) dikaji dengan cara diverifikasi berdasarkan kategori hujan dikotomi, lebat dan sangat lebat terhadap data dari 25 titik pengamatan di Jakarta. Prosedur yang sama juga diterapkan pada prakiraan curah hujan model Weather Research and Forecasting (WRF) dengan teknik multi-nesting yang di-downscale dari keluaran global forecast system (GFS). Hasilnya memperlihatkan bahwa kedua metode prediksi tersebut memiliki akurasi yang baik untuk prediksi dikotomi tetapi hampir gagal dalam memprediksi curah hujan lebat dan sangat lebat. Khususnya, kegagalan prediksi operasional dalam mendeteksi tiga kejadian hujan sangat lebat dalam periode kajian. Dalam hal ini, model WRF yang cenderung menghasilkan false alarm memperlihatkan prospek yang bagus untuk pengembangan sistem prediksi cuaca skala lokal/regional yang lebih akurat di Indonesia.

ABSTRAKDari data curah hujan di pantai barat Sumatera bagian utara dilakukan analisis spektrum daya untuk mengetahui pola curah hujan di daerah tersebut, selanjut dilihat hubungannya dengan intensitas monsun, Indian Ocean Dipole Mode (IODM), dan El-Nino Southern Oscillation (ENSO). Hasil analisis menunjukkan bahwa pola curah hujan di pantai barat Sumatera bagian utara memiliki dua puncak dan sangat dipengaruhi oleh faktor cuaca dengan dengan osilasi satu tahunan (annual oscillation), dan setengah tahunan (semi-annual oscillation) dan ditemukan hubungan yang kuat antara variabilitas monsun dan IODM. Pola hujan didaerah ini tidak memperlihatkan pengaruh ENSO.Kata Kunci : Curah Hujan, monsun, IODM, ENSO. ABSTRACTThe data of Rainfall in the west coast of northern Sumatera were analyzed through power spectrum analyzer to find out the rainfall pattern in that area and to look at the relationship between rainfall pattern and monsoon intensity, Indian Ocean Dipole Mode (IODM), and El-Nino Southern Oscillation (ENSO). The result of this analysis shows that the main rainfall pattern in the west coast of northern Sumatera has two peaks and is very much influenced by the factor of weather with annual oscillation and semi-annual oscillation, there is a strong relationship between monsoon variability and IODM, and the influence of ENSO on the rainfall in this region is not significant.

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On March 2, 2020, the first Coronavirus Disease (COVID-19) case was reported in Jakarta, Indonesia. One and half month later (15/05/2020), the cumulative number of infection cases was 16496 with a total of 1076 mortalities. This study is aimed to investigate the possible role of weather in the early cases of COVID-19 incidence in six selected cities in Indonesia. Daily data of temperature and relative humidity from weather stations nearby each city were collected during the period 3 March - 30 April 2020, together with data of COVID-19 cases. Correlation tests and regression analysis were performed to examine the association of those two data series. In addition, we analysed the distribution of COVID-19 with respect to weather data to estimate the effective range of weather data supporting COVID-19 incidence. Our results reveal that weather data is generally associated with COVID-19 incidence. The daily average temperature (T-ave) and relative humidity (RH) presents significant positive and negative correlation with COVID-19 data, respectively. However, the correlation coefficients are weak with the strongest correlations found at 5 day lag time i.e. 0.37 (-0.41) for T-ave (RH). The regression analysis consistently confirmed this relation. The distribution analysis reveals that the majority of COVID-19 cases in Indonesia occurred in the daily temperature range of 25-31oC and relative humidity of 74-92%. Our findings suggest that COVID-19 incidence in Indonesia has a weak association with weather conditions. Therefore, non-meteorological factors seem to play a larger role and should be given greater consideration in preventing the spread of COVID-19.