Seasonal assessment of fire weather index (FWI) in the forest regions of Iran using an ensemble of ECMWF-ERA5

Since one of the important steps in the management of natural areas is to know when and where the wildfire is more likely to occur or where it has a more negative effect, examining and preparing a fire risk map of sensitive and high-risk areas is crusial. In terms of wildfires, this is one of the main necessities in wildfires control and management. Wildfire risk indicators can be very useful for predicting areas with wildfire risk potential. One of the most widely used wildfire risk indices is the Forest service fire Weather Index (FWI), which has been based on the Canadian forest service fire risk rating system since 1971.In order to evaluate the effectiveness of FWI indicators in identifying wildfire-prone areas in the vegetation areas of Iran from the climate variables of temperature, relative humidity, wind speed, and precipitation of 53 meteorological stations were monitored on a daily basis for the period of 1981-2020. In order to analyze the climate of the vegetation areas under investigation, combined satellite product of burned areas and FWI indices during the period (1981-2020) were used. After downloading and an initial processing, the examined indicators were coilculated for the border of Iran. Then, their time series was analyzed, using zonal statistics. Than the area-averaged of each of Iran's forest regions was calculated, and their seasonal maps were prepared by the kriging interpolation method. Finally, the Pearson correlation coefficient method was used to determine the relationship and correlation between FWI indices and burned areas.The results of the analysis of the combined satellite product of the burned areas showed that the maximum extent of wildfire in the forest regions of Iran is related to the summer season. In this season, a large part of the country's forests, especially in the forest regions of Arsbaran, that has the occurrence of wildfires, and the minimum amount of wildfire was related to the spring season, which was observed in a limited area in the southwest of Iran. The values of atmospheric fire indicators vary according to the different characteristics of forest regions such as vegetation, topography, and climate. The drier parts of the south, east, and southeast of Iran mainly have the highest values of FWI indices, which shows that the increase in temperature and drought affects the moisture content and, as a result, increases the occurrence and spread of fire. The FWI indices in spring for all forest regions of Iran have a high efficiency for identifying areas with wildfire occurrences. Also, in the hot season of the year, when most wildfires occur in the vegetation areas of Iran, FFMC and FWI indices had the best performances.According to the climate variability and topography of Iran's forests, it is difficult to control the occurrence of fire. Hence identifying wildfire critical areas, and determining and preparing a map of fire-risk areas is an effective step in helping forest managers to plan and manage high-risk areas in terms of fire. In addition to this, wildfire atmospheric indices obtained with high horizontal resolution can help better understand the spatiotemporal variability of fire risk, especially in Iran with its complex and diverse topography.