Reanalysis of ECMWF data for updating the Fire Weather Index for the Indonesia Fire Danger Rating System (InaFDRS)

Fire Weather Index (FWI) as one of the parameters of the Fire Danger Rating System (FDRS) was developed about 80 years ago. The most widely adopted index is the Canadian FWI. The FWI requires daily temperature, humidity, and wind speed measured at local noon, and accumulation of rainfall over the last 24 hours. Since 2018, FWI has been measured for the Regency of Ogan Komering Ilir (OKI), South Sumatra District. To supplement the sparse weather stations, we used the daily ECMWF (European Centre for Medium-Range Weather Forecasts ) reanalysis from 1979 to 2018 to calculate the FWI values. Data reanalysis using power spectral density function show intra-seasonal cycles (5.9 months) and annual cycles (11.9 months) of monsoons, and 3- year cycles detected from Indian Ocean Dipole (IOD) phenomena and cycles of El Niño Southern Oscillation (ENSO) phenomena with repeat signals every 1.5, 3.5, 5.5, and 9.75-years cycle. The pattern of changes in the FWI time series values follows the local weather system, the regional climate system (monsoon), the climate system in the Indian Ocean with its IOD phenomenon, and the tele-connected climate system in the Pacific Ocean, ENSO phenomenon. Based on this pattern, an updated FWI classes was determined to better fit the climate condition of Indonesia, specifically OKI Regency that yield a better rating for the FDRS