利用同化资料改进WRF-Chem对华北地区秋季PM_(2.5)预报的研究  

Improving the WRF-Chem forecast of PM_(2.5) over North China in autumn with data assimilation

作　　者：李文凯 陈耀登[1] 陈丹[2] LI Wenkai;CHEN Yaodeng;CHEN Dan(Key Laboratory of Meteorological Disaster,Ministry of Education/International Joint Laboratory on Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science and Technology,Nanjing 210044,China;Institute of Energy,Peking University,Beijing 100871,China)

机构地区：[1]南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心,南京210044 [2]北京大学能源研究院,北京100871

出　　处：《气象学报》2024年第5期659-671,共13页Acta Meteorologica Sinica

基　　金：国家重点研发计划重点专项项目(2022YFC3004003);国家自然科学基金(42075148)。

摘　　要：气溶胶初始场同化能够提高WRF-Chem气象-气溶胶耦合预报的准确度。为了讨论气溶胶同化在不同时刻对耦合模式预报的影响,针对2015年10月一次重度霾污染过程,进行了一天4个不同时刻的气象-气溶胶联合同化及短时预报试验研究。结果表明,在同化气象资料的基础上同化气溶胶观测资料能够改善不确定性较大的排放源清单带来的模拟高估问题,减小初始场PM_(2.5)的正偏差;随着初始场PM_(2.5)浓度的下降,气溶胶导致的地面辐射的下降减弱,使得日间时刻6 h预报场的向下短波辐射量增加;日间近地面温度和湿度对辐射量变化的响应(增温减湿)呈现为在空间大面积上的重合和时间上的同步,这种响应在循环滚动预报的影响下即使在夜间也得到了延续;近地面增温减湿的结构有助于边界层向上发展,从而促进气溶胶的向上传输,最终进一步减弱预报场对地表PM_(2.5)的高估。因此,气溶胶同化带来的初始场PM_(2.5)信息的改善,使得6 h耦合预报的结果更加准确。Assimilation of the initial aerosol field can improve the accuracy of coupled meteorology-aerosol forecasts in WRFChem.To discuss the influence of aerosol assimilation on coupled model forecasts at different times for a heavy haze pollution process in October 2015,an experimental study of joint meteorology-aerosol assimilation and short-term forecast at four different times of a day was conducted.The results show that assimilating aerosol observations on the basis of assimilated meteorological data can improve the overestimation of simulation caused by the emission source inventory with large uncertainty,and reduce the positive bias of PM_(2.5) in the initial field.With decreased PM_(2.5) concentration in the initial field,the reduction of surface radiation caused by aerosols is weakened,which increases downward shortwave radiation in the 6 h forecast in the daytime.The response of near-surface temperature and humidity to radiation changes(warming and humidity reduction) during the daytime is spatially coincident over a large area and temporally synchronized,and continues even at night under the influence of circular rolling forecast.The structure of the near-surface warming and humidity reduction contributes to upward development of the boundary layer,which in turn promotes upward transport of aerosols and ultimately attenuates the overestimation of surface PM_(2.5) in the forecast.Consequently,the improvement of the initial PM_(2.5) information due to aerosol assimilation makes the 6 h coupled forecasts more accurate.

关 键 词：WRF-Chem WRFDA-Chem 气象-气溶胶联合资料同化 耦合预报 

分 类 号：P456.7[天文地球—大气科学及气象学]