WRF-CMAQ model was used to simulate a severe PM_(2.5) pollution episode in Qingdao from 1 to 7 January, 2016, and the major factors influencing the formation, persistence and removal of the severe PM_(2.5) pollution were analyzed. The model reasonably reproduced the temporal and spatial variation of PM_(2.5) concentration and meteorological conditions. Under the influence of persistent southwest airflow during the severe pollution formation period, PM_(2.5) and its precursors were transported to Qingdao fro...