Evaluation of Global Fire Weather Database re-analysis andshort-term forecast products

Abstract. Daily Fire Weather Index (FWI) System components calculated from the NASA he Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) are compared to FWI calculations from a global network of weather stations over 2004-2018, and short-term, experimental (8-day) daily FWI forecasts are evaluated for their skill across the Terrestrial Ecoregions of the World for 2018. FWI components from MERRA2 were, in general, biased low compared to station data, but this reflects a mix of coherent low and high biases of different magnitudes. Biases in different MERRA2 FWI components were related to different biases in weather input variables for different regions, but temperature and relative humidity biases were the most important overall. FWI forecasts had high skill for 1–2 day lead times for most of the world. For longer lead-times, forecast skill decreased most quickly at high latitudes, and was most closely related to decreasing skill of relative humidity forecasts. These results provide a baseline for the evaluation and use of fire weather products calculated from global analysis and forecast fields.