Abstract:

Based on the conventional meteorological data from national meteorological stations in Nanchang from 1960 to 2014 and atmospheric pollutant observations from environment protection department from 2001 to 2014,an Eta correlation coefficient method and a regression analysis method were used to study the characteristics of meteorological parameters and main atmospheric pollutants of haze as well as the relationship between haze and atmospheric pollutants in Nanchang.The results show that annual haze days in Nanchang gradually increase from 1960 to 2014,and they occur mostly in autumn and winter but less in spring and summer.The averaged surface wind speed is 1.6 m·s^-1 at 08:00 of haze days in recent 55 years in Nanchang,and the northeasterly winds prevail.Such small wind speed favors the formation and development of haze weather.The averaged surface air pressure at 08:00 of haze days mostly ranges in 1010-1025 hPa,with a mean value of 1015.3 hPa.The values of temperature-dew point depression at 925 hPa are larger in the northern region and smaller in the southern region.Winds blow from the dry area to the Nanchang region that is located at the bottom of a dry tongue at lower altitudes.The northeasterly flow prevails at 925 hPa,with wind speed concentrating in 3.0-8.0 m·s^-1.The distribution of wind speed at 850 hPa is consistent with that at 925 hPa.Air flows divergence at lower altitudes (at 925 hPa) and a weak through at the middle altitudes (at 500 hPa) located before the Nanchang region form a favorable weather situation for haze occurrence.There are 59.1% and 45.3% of haze days with thermal inversion layer between surface and 850 hPa at 08:00 and 20:00,respectively.Inversion layer makes astable atmospheric condition that favors haze development.Concerned for main air pollutants in Nanchang,the monthly mean concentrations of PM₁₀,NO₂,SO₂,and PM_2.5 show the maximum value in December and January and the minimum value in July and August,which is consistent with the seasonal variation of haze.Pollutant concentrations of haze days are obviously larger than those of non-haze days.According to the Eta correlation analysis,the correlations between daily mean concentrations of four pollutants and haze decrease in order of PM₁₀,PM_2.5,NO₂,and SO₂.The correlation coefficient between PM₁₀ concentration and haze is 0.694,which means a strong correlation.

Key words: Haze, Meteorological parameter, Temperature inversion, PM₁₀, PM_2.5, Correlation analysis