Uncertainties Quantification And Key Uncertainties Identification Of Nitrate Aerosol Simulation

Nitrate aerosol is an important component of PM_2.5,as anthropogenic NO_x and NH₃ emissions increase,SO₂ emissions decrease the proportion of nitrate in PM_2.5 gradually increases.Affected by uncertainties of input parameters of model and model structures,the nitrate aerosol simulation still has large biases.However,currently no researchs apply quantitative uncertainty analysis to diagnose nitrate simulation,and the key uncertainty sources of nitrate simulation are not yet clear.Moreover,the existing researchs on the uncertainty of aerosol simulation only consider the influence of the model input parameters uncertainty on the simulation and ignore the influence of the model structure uncertainty,which may miss important uncertaninty sources of nitrate simulation.According to the above limits,we built a WRF/SMOKE-PRD/CMAQ simulation system,takeing sensitivity and uncertainty analysis as method,and uncertainty transfer method of an ensemble simulation and Monte Carlo based on a simplified model was applied to to quantify the impact of uncertainties of input parameters of model and model structures,and identify the key uncertainty sources of nitrate simulations.The main findings are as follows:1)Different N₂O₅ heterogeneous reactions,aerosol chemical reaction and CMAQ versions had significant effects on nitrate simulation,and gas-phase chemical reactions had weaker effects on nitrate simulation;2)NO_x emissions,NH₃ emissions,boundary conditions O₃ concentration,temperature and wind speed were important sensitive input parameters that affected the nitrate simulation;3)Uncertainty of model input parameters and model structure of the Pearl River Delta nitrate simulation were equivalent.The uncertainty range of the nitrate simulation related to the input parameters and structural uncertainties can cover 70.08%of the observation data,and compared with night,uncertainty of nitrate simulation was greater during the day;4)Among model input parameters,wind speed,temperature,NH₃ emissions and lateral boundary conditions of O₃were the key uncertainty sources of nitrate simulation,and the proportion of uncertainty contributions of them are 31.26%,22.45%,21.72%and 20.65%respectively.Among model structures,the proportion of nitrate simulation uncertainty contributions of CMAQ version,N₂O₅heterogeneous mechanism,aerosol mechanism were 52.68%,30.36%and 16.96%respectively.Due to the different generation mechanisms of nitrate,there were obvious diurnal differences in the nitrate simulation uncertainty contribution of different model input parameters and model structure.During the day,the impact of uncertainties of NH₃ emissions,temperature,CMAQ version,aerosol mechanism on nitrate simulation increased.At night,the impact of uncertainties of wind speed,lateral boundary conditions of O₃,N₂O₅ heterogeneous mechanism on nitrate simulation increased;5)Overall,reducing uncertainty of wind speed,NH₃ emissions and lateral boundary conditions of O₃ and choosing the best CMAQ version and N₂O₅ heterogeneous mechanism can improve the accuracy of nitrate simulation.Focus on reducing the uncertainty of nitrate simulation during the day by reducing uncertainty of wind speed,NH₃ emissions and temperature and choosing best CMAQ version,aerosol mechanism can more effectively improve the nitrate simulation effect.