Abstract: Based on available observation data of Hefei Meteorological Station from 1952 to 2016 and the 
daily ground and altitude observation data from 2004 to 2016, the characteristics of haze day 
and related meteorological elements are analyzed. Then combining with the air pollution 
data of Hefei from 2004 to 2016, the prediction equations of haze day and the visibility in 
haze day are obtained preliminarily. Finally, the forecast results are verified by using the 
meteorological and air quality data of 2017. The results show that haze in Hefei is dominated 
by slight haze and mild haze, and the haze days distribute unevenly month by month, with the 
most haze days in January and December. The growth and elimination of haze have diurnal changes. 
Haze occurrs mainly at 11 to 20 o'clock every day. The favorable meteorological conditions for 
haze day are as follows: wind speed is less than 3 m/s, the leading wind direction is easterly 
or southerly, with negative pressure, positive temperature and relative humidity of 50$\sim$70\%. 
Low visibility haze requires high relative humidity and negative pressure. It is shown that the 
prediction equations have high accuracy, which can provide some reference for haze forecasting in Hefei.

Key words: haze, visibility, meteorological elements, forecast