Characteristics of haze weathers with different level in Shenzhen during 1981～2010

Based on the observational haze data and the air environment quality data in Shenzhen during 1981～2010,the long-term variation tendency of the haze weather with different level was analyzed along with the relationship between the haze weather and the atmospheric visibility,air quality.The annual haze days of Shenzhen showed an increasing trend overall.At the same time,the numbers of the haze days at each level,such as slight,mild,moderate and severe,also showed an increasing trend.The proportion of the slight haze declined,while the proportion of the haze over the mild level rose over the 30 years.For different seasons,the maximum occurrence probability of haze weather was recorded in winter,followed by autumn,spring and summer sequentially.However,the severe level of haze happened mostly in summer.The occurrence of the haze weather often led to the descending of the atmospheric horizontal visibility that average visibility during haze days was about 6～7km lower than it in non-haze days, and a higher level of haze often result in a lower visibility.The air quality monitoring data suggested that the SO2,NO2concentrations during haze days were 1.4～1.7 times of those in the non-haze days,while the PM10concentration was 2.2 times,which indicated the increase of atmospheric particulate pollution was possibly one important reason of haze increasing.For Lixiang Station,PM10 and NO2concentrations during haze days exhibited a bimodal diurnal variation characteristics which was accordant with the rush hours,which suggested that the increasing number of the motor vehicles contributed to haze weather in Shenzhen.The data also showed that the higher the haze level was,the higher of the PM10,SO2 and NO2concentrations, and the increase of the PM10,SO2 and NO2concentrations between each haze level was about 15%～20%.