Objective To Study the impacts of the El Niño/La Niña events on the fire weather of Daxing'anling so as to improve the accuracy of fire danger forecasting.

Method The values of fire weather index during 1951-2016 were calculated including the daily maximum temperature, the minimum relative humidity, the average wind speed, and the 24-hour precipitation collected by weather stations in the study area, and the differences of the weather and fire weather indices under four scenarios of the super strong and strong El Niño, moderate and weak El Niño, La Niña and normal years were analyzed respectively.

Result Compared with the normal year, the average daily maximum temperature in the spring fire season in super strong and strong El Niño years decreased by 0.21℃, and precipitation increased by 6.78%. In spring fire season of La Niña years, the average daily maximum temperature was 0.44℃ higher, and the precipitation increased by 2.77mm. The daily maximum temperature of autumn fire season in El Niño/La Niña years was lower than that of the normal years. The average of fine fuel moisture code (FFMC), duff moisture code (DMC), drought code (DC), build up index (BUI) and fire weather index (FWI) in spring and autumn fire season under the situations of super strong and strong El Niño event were lower than those in normal years, and the FWI gradually decreased from southwest to Northeast. All six component fire weather indices of spring fire season in moderate and weak El Niño years were lower than those in normal years and also lower in autumn fire season except FFMC. In La Niña years, the FFMC, the initial spread index (ISI) and the FWI of spring fire season were lower than those of normal years, and all the indexes were lower than those in normal years as well, except for DC.

Conclusion The forest fire weather index of super strong and strong El Nino in spring and autumn fire season was lower than that of the normal years in Daxing'anling, and the index of the western region was higher than that in the eastern region. In La Niña year, The FWI in spring fire season in the eastern region was lower than normal years and higher in the midwest. The FWI was higher than the normal years in northwest region and lower in southeastern in autumn fire season.