The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianji...The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianjin Hebei experienced a seven-day extreme haze pollution episode with peak PM2.5(particulate matter(PM)with an aerodynamic diameter≤2.5μm)concentration of 727μg m 3.Considering the in uence of meteorological conditions on pollu-tant evolution,the e ects of varying initial conditions and lateral boundary conditions(LBCs)of the WRF-Chem model on PM2.5 concentration variation were investigated through ensemble methods.A control run(CTRL)and three groups of ensemble experiments(INDE,BDDE,INBDDE)were carried out based on difierent initial conditions and LBCs derived from ERA5 reanalysis data and its 10 ensemble members.The CTRL run reproduced the meteorological conditions and the overall life cycle of the haze event reasonably well,but failed to capture the intense oscillation of the instantaneous PM2.5 concentration.However,the ensemble forecasting showed a considerable advantage to some extent.Compared with the CTRL run,the root-mean-square error(RMSE)of PM2.5 concentration decreased by 4.33%,6.91%,and 8.44%in INDE,BDDE and INBDDE,respectively,and the RMSE decreases of wind direction(5.19%,8.89%and 9.61%)were the dominant reason for the improvement of PM2.5 concentration in the three ensemble experiments.Based on this case,the ensemble scheme seems an e ective method to improve the prediction skill of wind direction and PM2.5 concentration by using the WRF-Chem model.展开更多
Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectr...Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.展开更多
基金supported by the National Basic Research(973)Program of China [grant number2015CB954102]the National Natural Science Foundation of China [grant number 41475043]the National Key R&D Program of China [grant number 2018YFC1507403]
文摘The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianjin Hebei experienced a seven-day extreme haze pollution episode with peak PM2.5(particulate matter(PM)with an aerodynamic diameter≤2.5μm)concentration of 727μg m 3.Considering the in uence of meteorological conditions on pollu-tant evolution,the e ects of varying initial conditions and lateral boundary conditions(LBCs)of the WRF-Chem model on PM2.5 concentration variation were investigated through ensemble methods.A control run(CTRL)and three groups of ensemble experiments(INDE,BDDE,INBDDE)were carried out based on difierent initial conditions and LBCs derived from ERA5 reanalysis data and its 10 ensemble members.The CTRL run reproduced the meteorological conditions and the overall life cycle of the haze event reasonably well,but failed to capture the intense oscillation of the instantaneous PM2.5 concentration.However,the ensemble forecasting showed a considerable advantage to some extent.Compared with the CTRL run,the root-mean-square error(RMSE)of PM2.5 concentration decreased by 4.33%,6.91%,and 8.44%in INDE,BDDE and INBDDE,respectively,and the RMSE decreases of wind direction(5.19%,8.89%and 9.61%)were the dominant reason for the improvement of PM2.5 concentration in the three ensemble experiments.Based on this case,the ensemble scheme seems an e ective method to improve the prediction skill of wind direction and PM2.5 concentration by using the WRF-Chem model.
基金supported by the project "Investigation of Climate Change Mechanisms by Observation and Simulation of the Polar Climate Past and Present" (PE14010) of the Korea Polar Research Institutethe National Natural Science Foundation of China (Grant No.41375003)the Beijing High Education Young Elite Teacher Project and the Chinese Academy of Sciences (Grant No.XDA05110303)
文摘Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.
