Abstract: The annual and daily variation of haze weather during heating periods,and the variation of the corresponding meteorological elements were analyzed using the ground observation data in Shenyang from 1980 to 2015.The results show that the number of haze days during heating periods demonstrates a steady increasing trend from 1980 to 2015.The haze weather mainly appears from 07:00 to 11:00 a.m.,mostly disappears at night and in the afternoon.The duration of most of haze weathers is within 7 hours.When the haze weather happens during heating periods,the relative humidity on the ground is high and regularly in the range of 70%- 90%.The wind on the ground is often static,its speed is commonly less than 3.0 m·s^-1,and its direction is mostly easterly.The height of mixing layer calculated by the surface observation data has a good indication effect to the different ranks of haze weathers.For the severe haze weather,the height of mixing layer is frequently within 0-400 m;for the moderate one,it is within 0-600 m;and for the mild one,it is within 200-600 m.To strengthen the monitoring and forecasting of weather conditions can help to effectively predict haze weathers and to take useful measures to reduce the haze influence.

Key words: Heating periods, Haze, Temperature inversion, Height of mixing layer