Calibration and evaluation of the Forest Fire Weather Index (FWI) in the Hamoun wetland area

Wetlands are important global ecosystems that are expected to be very vulnerable to fires caused by climate change. The adverse effects of climate in recent years have increased the fire occurrence danger in Hamoun wetland. One of the methods of predicting the occurrence of fire is the use of fire weather indicators such as FWI. This index, which is widely used all over the world, evaluates the effect of these factors on the risk of fire by considering air temperature, relative humidity, wind speed, and precipitation. In this study, after preparing FWI daily raster layers in the Hamoun wetland, new thresholds for different classes of fire danger were estimated. Then, the ability of the FWI index to predict the occurrence of fire based on new thresholds was done. Among the meteorological parameters, the monthly average wind speed has the highest correlation with the monthly changes in the FWI index. The average total value of FWI is more than 70. The cumulative distribution of FWI values in the region showed that for 75% of days (between 1998 and 2021) FWI value is greater than 47. The value of FWI for the northern areas is much higher than the southern areas. The results of the Mann-Kendall trend test show the increasing trend of FWI. The results showed that there is a significant difference between the new thresholds and the standard threshold values. So that the very high danger threshold, which is equal to 38 in standard conditions, has reached 105. Validation results showed that the AUC criterion in predicting the very high danger of fire, considering the new threshold, will reach from 0.576 to 0.834 in standard conditions. It can be said that the new threshold of FWI has been able to predict the danger of fire in the Hamoun wetland with good and acceptable accuracy.