Abstract: Based on the hourly visibility data from 2002 to 2011 in Lvshun of Liaoning province and Longkou of Shandong province, the daily, monthly and annual visibility characteristics were analyzed by a grade analysis method. The results indicate that the annual mean visibility is higher in Lvshun than in Longkou, and both averages are in decreasing trends in the recent decade, especially in Longkou. The time percentage of annual visibility in the different levels changes significantly in Lvshun, while it is stable in Longkou. The maximum visibilities in both locations appear in October, while the minimum value occurs in July in Lvshun and June in Longkou, respectively. The monthly visibility characters are similar in Lvshun and Longkou, and each has one peak and one valley. Analysis of weather phenomenon and corresponding meteorological elements shows that the regional differences are significant for wind field, temperature and relative humidity field in Lvshun and Longkou when visibility range is from 0 to 1 km.

Key words: Lvshun, Longkou, Visibility, Temporal and spatial change