Characteristics and Causes of Foggy Days in Winter over Hainan Island

Based on the daily data of 18 national meteorological observatories in Hainan Island from 1981 to 2018 and NCEP/NCAR wind reanalysis data, the circulation field of more or less foggy days were synthesized and analyzed, and the fog event in Hainan Island in February 2018 was analyzed. The results show that the more days event is 1968, and the foggy days are about 21 days in Hainan Island; the least is 2011, and the foggy days are about 5 days in Hainan Island; the more foggy days in winter correspond to the abnormal upper-level westward flow, middle and lower atmosphere of Hainan Island; the fewer foggy days in winter correspond to the abnormal eastward upper-level flow, middle and lower atmosphere of Hainan Island. The abnormal westward flow in the upper, middle, and lower atmosphere correspond to the severe fog event in Hainan Island in February 2018, which is consistent with the climatic causes.