Research On Numerical Simulation Of Dust Storms In Northwest Region And Their Effects On Atmospheric Environment In Typical City

As a disastrous weather,sand and dust weather can be classified into five categories:floating dust,blowing sand,sandstorm,strong dust storm and super strong dust storm.Dust and dust weather has brought about important changes in regional and global climate change,and has a serious impact on air quality,human health and traffic safety.Dust weather is one of the urgent problems to be solved in our country at present.Therefore,it is of great practical significance to strengthen the research on dust weather.In this paper,the WRF-Chem air quality model is used to simulate the sand dust process in Northwest China by coupling five different parameterization schemes,and the results are compared with the observed data.The simulation ability of the WRF-Chem model to the sand dust process is preliminarily verified,and the similarities and differences of the simulation of the sand dust process under the five different sand raising parameterization schemes are analyzed.Secondly,By adjusting the value of key parameters in the formula of sediment fluxes under the Shao11parameterization scheme,and analyzing the influence of different soil moisture on the simulation of sand dust process,the optimum configuration of sediment raising parameters and soil moisture are found out.Finally,the influence of dust weather on air quality in Lanzhou is discussed.The main conclusions are as follows:?1?The WRF-Chem model,which is coupled with five different parameterization schemes,such as GOCART,AFWA,Shao01,Shao04 and Shao11,can well reproduce the temporal and spatial evolution characteristics of dust concentration,the main sand raising area and the sand dust transport process.Compared with the simulated results under the two sand lifting schemes of GOCART and AFWA,the simulated dust distribution under the three schemes of Shao01 and Shao11 is wider,and in some areas,the dust concentration and sediment flux are larger.Under the five schemes,the time variation characteristics of PM₁₀0 mass concentration in the simulated source area and the affected area are very close to the observed results,but for different sand and dust processes,The peak value of PM₁₀0 mass concentration and the observed peak value of PM₁₀0 simulated by different sediment raising schemes are different.In general,the simulation results of PM₁₀0 mass concentration by WRF-Chem model based on Shao11 scheme are superior to those of GOCART,AFWA,Shao01 and Shao04 schemes.?2?The change of weight factor and sediment rising adjustment factor related to particle size distribution have no obvious influence on the distribution range of dust and sediment flux,but have great influence on dust concentration,sediment rise flux and PM₁₀0 mass concentration.With the decrease of the value,the dust concentration,sediment flux and PM₁₀0 mass concentration are increased.Compared with?is 0.5 or 0,the model has the best ability to simulate the mass concentration of PM₁₀0 when?is equal to 1.With the decrease of the value of c,the simulated values of dust concentration,sediment flux and PM₁₀0 mass concentration also decrease.The simulation ability of the model for sand and dust processes in different locations is different under different values of c.Compared with c is 1.5 or 1,the model has the best ability to simulate the mass concentration of PM when c is equal to 2.6.?3?The soil moisture of surface 0¹0cm in the GLDAS data of Northwest China is lower than that of NCEP as a whole.Soil moisture in GLDAS data is generally below 0.32m³/m³,while in NCEP data,soil moisture is 0.08⁰.48m³/m³.With the GLDAS data,the distribution of the simulated sand dust and sediment area is wider,and the dust concentration,sediment fluxes and PM₁₀0 mass concentration are larger.Because the soil moisture provided by GLDAS data is low,and the critical friction velocity is also low,the model simulated more sand dust emissions under the same wind speed.But the soil moisture under NCEP data has better simulation ability to simulate the evolution characteristics of PM₁₀0 mass concentration during the process of sand and dust.?4?The evolution of SO₂,NO₂ and CO concentrations in Lanzhou is divided into two types:displacement and superposition.The displacement type is affected by the strong cold air activity.With strong northeast wind near the ground and the system of low temperature and high pressure,the concentration of SO₂,NO₂ and CO decreases significantly.The dust source is mainly located the Taklimakan desert in the southern Xinjiang basin and the northern part of the Qinghai-Tibet Plateau.The north-west airflow at the height of 1500-1600 meters has the greatest impact.The superposition type is affected by the weak cold air activity,with the weak northeast wind near the ground and the air temperature and air pressure have no obvious fluctuation,the initial PM₁₀0 and PM_2.5.5 concentrations increase,while the SO₂,NO₂ and CO concentrations decrease slightly,and then the PM₁₀0 and PM_2.5.5 maintain high values.The concentration of SO₂,NO₂ and CO increased due to the continuous accumulation of gaseous pollutants from the local sources.The sources of sand dust are mainly in the Badain Jilin Desert in Inner Mongolia and the local sand dust area,and The north-west airflow Below 1500 meters has the greatest impact.The WRF-Chem model can well simulate the variation characteristics of PM₁₀0 mass concentration and meteorological elements and the dust sources during the replacement and superposition types of sand and dust weather.