20IMPACTS Comparative Analysis on Meteorological Condition for Two Serious Pollution Events in Liaoning Province Caused by Crop Residue Burning

Based on pollutant data from environmental monitoring stations, observational data from surface automatic meteorological station, L-band sounding second data and 0.125°×0.125° EC reanalysis data, together with fire points data from satellite remote sensing and simulation results of HYSPLIT4 backward trajectory, planerary boundary layer features, diffusion and transport meteorological conditions of two serious pollution events in Liaoning province caused by crop residue burning of northeast China in early November 2015 (November 8, 2015) and 2016 (November 5, 2016) was analyzed. The result shows that pollutant concentrations increased and decreased rapidly during the two pollution events, The serious pollution event on 8 November 2015 has a stronger intensity and a longer duration than the event on 5 November 2016; In event on 8 November 2015, mixing height was lower, on which neutral layer changed into inversion layer restraining development of mixing layer height. Cold advection in lower layer invaded below warm advection in higher layer, making the atmosphere more stable and lasting longer. Enhanced vertical subsidence motion and long-distance horizontal regional transportation of pollutants in southwest Heilongjiang and western Jilin province resulted in rapid accumulation of pollutants on the ground in Liaoning; Due to stronger cold air, regional transportation in west of northeast China and ground wind convergence strengthened, is the main reason for the rapid increase of pollutant concentration in event on 5 November 2016.