Study On The Influence Of Complex Terrain On The Wind Field And The Tropospheric Ozone Concentration

Complex terrain has an important influence on the spatial and temporal distribution of wind field and the change of atmospheric composition in the boundary layer.However,numerical simulation can help us to obtain the wind field laws under different terrain micro-environment and spatial and temporal distribution characteristics of atmospheric composition concentration.Therefore,this study takes Dali,Yunnan Province and alert city of the Arctic as examples to carry out a three-dimensional numerical study on the change of wind field and the termination process of ozone depletion on a small spatial scale under the condition of complex terrain,so as to evaluate the influence of complex terrain on the temporal and spatial distribution of wind field and its role in the termination process of ozone depletion in the Arctic.The main conclusions of this article are as follows:(1)Under the condition of micro environment topography in the south of Dali Bai Autonomous Prefecture,Yunnan Province(100.24 ° N,24.83 ° E),when the south wind blows in this area,the local wind speed will increase due to the forced uplift of the terrain at the windward slope,and the maximum value is close to 1.5 times of the inlet wind speed.At the same time,due to the blocking effect of mountains,the wind speed on the back slope of the hillside will sharply reduce,and the wind direction will also change,resulting in small-scale vortex and irregular return flow.After calculation,the wind speed at the center detection point is smaller than that at the entrance when the north wind blows,while the wind speed at the detection point is slightly higher than that at the entrance when the east wind blows.In addition,under the condition of westerly wind,the variation of wind speed at the observation point is the largest.When the initial inlet wind speed is 30 m/s westerly,the maximum component of wind speed at the observation point in the horizontal direction can reach 44.55 m/s after 7200 seconds.(2)When the Arctic alert city blows southward,the wind from the South needs to cross the 700 m peak.At the windward slope of the peak,the wind speed increases due to the forced lifting of the terrain,and there is a trend of attenuation at the leeward slope after the wind blows over the peak,and the wind speed attenuation degree caused by different heightsof the peak is different.The higher the slope,the greater the attenuation of wind speed.When ozone depletion occurs in the Arctic,the wind blowing over the mountain will lift the air with very low ozone concentration at the bottom of the study area,and mix with the air with high ozone concentration at the high altitude.However,the downdraft on the leeward slope will mix the air with high concentration of ozone at high altitude with the air with low concentration of ozone on the surface near the ground,resulting in the increase of ozone concentration on the leeward slope and the termination of ozone depletion.It is also found that the higher the mountain height is,the stronger the ozone mixing intensity is at the leeward slope.