Research On Surface Wind And Forest Fire Simulation In Liangshan, Sichua

In recent years,forest fires occur frequently.It is very important to study forest fire spread behavior under complex terrain to protect ecosystem and residents’ safety.Wind is the main physical quantity of the near-ground atmosphere,and also an important factor affecting forest fire spread.In this paper,the near-surface wind field and forest fire spread behavior around the "March 28" forest fire in Muli in 2020 was taken as the research object.Firstly,based on the mesoscale numerical model WRF,NASADEM topographic data with a resolution of 30 m and FROM＿GLC surface cover data with a resolution of 30 m are added into the sub-grid.The sensitivity test of six boundary layer parameterization schemes was carried out by adding topographic gravity wave dragging parameters.The results show that there is little correlation between model resolution and simulation error of near-surface wind field.The simulation error of YSU scheme and Shin-Hong scheme is the minimum for 10 m wind direction.The simulation error of YSU scheme and MYNN3 scheme is the minimum for 10 m wind direction.It is found that YSU,MYJ,QNSE and Shin-Hong schemes can simulate the distribution of wind field in the fire area by analyzing the simulation results of wind field in the fire area.By comparing the simulation results of temperature,specific humidity,wind speed and wind direction profile of Xichang Station,it is found that the simulation results of YSU scheme are closest to the observed values,and can better represent the dynamic and thermal structure in the boundary layer.Therefore,YSU scheme has the best simulation effect on near-surface wind field in Liangshan area and forest fire disaster area in Muli.Combined with YSU scheme,WRF-Fire model is adopted,and NASADEM topographic data with a resolution of 30 m and fuel data with a resolution of 30 m are added to the fire grid to simulate the "March 28" forest fire in 2020.The simulation results are compared with the actual fire field observed by GF1 satellite.The results show that the model can accurately reproduce the influence of near-surface wind field on the forest fire spreading process,and the fire spreading is also affected by terrain and combustible materials.The simulated spreading direction and fire area are basically consistent with the real fire.Due to some differences between actual near-surface meteorological data and simulation results,as well as actual fire-fighting behavior,there are errors between simulated and actual fire sites.In order to improve the simulation accuracy,the random forest algorithm was used to revise the simulation results by combining the surface meteorological,vegetation and topographic data.The results showed that the accuracy rate was improved from 78.79% to 83.29%after the correction.The effect of near-surface wind field on the modified fires is greater than that of topography,which affects the simulated fires more.Therefore,both the modified fire area and the no-fire area are closer to the actual observed data.