A Study on Long-term Change of Haze Days Based on Wavelet Transform and M-K Test

According to the haze data at 7 weather stations from 1971 to 2010 in Shiyan of Hubei province,the characteristics of haze change were analyzed using the methods of a linear trend analysis,a EOF and a M-K and a wavelet analysis,The results showed that in Shiyan haze days was maximum in December and minimum in July to September,the haze days in autumn and winter accounted for more than 70 percent of annual total haze days.In general,the number of annual haze days represent the obvious increasing trend,especially increasing rapidly after the 1990s,the haze days is Increased with a tendency of 5.9 days per 10 years.The change of annual haze days could be divided into five stages,among which haze days from middle to late 1990's and beginning of the 21 century were increasing rapidly.However the number of the haze days in Shiyan is still more and the annual average is 23.3d.From regional distribution,haze days were most in Danjiangkou,and next calne Yunxian,while Fangxian had fewest haze days.In the recent 40 years,the haze show remarkable interannual and interdecadal variability.There is remarkable haze period of 8 years.The most concentrated period of haze mutations was in 2002.