4.3      Retrospective analysis of 2015-2017 winter-time PM2.5 in China: response to emission regulations and the role of meteorology.

Chen, Dan, Institute of Urban Meteorology, China Meteorological Administration, Beijing, China, Zhiquan Liu, Junmei Ban, National Center for Atmospheric Research, Pusheng Zhao, and Min Chen, Institute of Urban Meteorology, China Meteorological Administration, Beijing, China

To better characterize the anthropogenic emission relevant aerosol species, the GSI-WRF/Chem data assimilation system was updated from the GOCART aerosol scheme to MOSAIC-4BIN scheme.
Three year (2015-2017) winter-time (January) surface PM2.5 observations from 1600+ sites were assimilated hourly using the updated 3DVAR system in the assimilation experiment CONC_DA.
Verifications against the surface PM2.5 observations, AERONET 550-nm AOD and MODIS 550-nm AOD show the reliability of the updated DA system.
The observations and the reanalysis data from assimilation experiment were used to investigate the year-to-year changes and revealed the PM2.5 concentration fluctuations although continuously emission reduction were expected.
The important roles of emission and meteorology in driving the changes in the three years were distinguished and quantitatively assessed. It approved that meteorology did played different roles in 2016 and 2017.