Abstract:

Observation data from the meteorological stations along Liaoning coastal expressway and the NCEP (National Centers for Environmental Prediction) reanalysis data from 2005 to 2018 were used to analyze the climatic characteristics of heavy fog along Liaoning coastal expressway and its relationship with relevant meteorological elements.The influence factors of circulation on heavy fog were also studied.The results show that the average annual heavy fog days of Liaoning coastal expressway has a high-low-high feature from west to east.The average number of the annual heavy fog days of east and south coast coastal expressway in Liaoning province is the largest.The average number of fog days along the east coastal expressway in the east of Liaoning province has a significant decreasing trend from east to west.The difference of the average number of the annual heavy fog days of each expressway station along the western Liaoning province is the biggest and the local influence on the western coastal expressway is the strongest.The average annual number of heavy fog days in coastal expressway has obvious monthly and seasonal variation characteristics.Heavy fog days occur most frequently in October and less in May.The highest proportion of the number of heavy fog days in the whole year occurs in autumn, and the lowest is in summer.The fogs in autumn are strong mainly appearing at the height from 0-200 m, with the temperature in 10-15℃, relative humidity more than 98%, wind speed between 0-3 m·s^-1, and northeastern wind prevailing.Based on the analysis of circulation characteristics, we conclude that the coastal areas in Liaoning province in autumn are less affected by the subtropical high and normally affected by the latitudinal circulation and polar vortex.The stronger or weaker the zonal circulation and polar vortex are, the more or less heavy fog days are in the coastal areas of Liaoning province.The water vapor comes from the eastern mountainous area of Liaoning province, the Bohai Sea, and the northern part of the Yellow Sea.The fog form along Liaoning coast expressway in autumn is not the sea fog, but the frontal and radiation fogs.The advection fog over the east coast of Liaoning province comes from eastern mountainous area of Liaoning province is also another form.

Key words: Coastal expressway, Heavy fog, Circulation characteristics