Relationships Between Dustfall And Meterological Factors In Industrial District Of Wusong, Shanghai

This paper investigated systematiclly variation characteristics of monthly dustfall and the relationships between dustfall change and meterological factors in industrial district of Wusong , Shanghai by the combination of statistical method, graphic illustration on the basis of monthly dustfall and corresponding meteorological factors from 1993 to 2003, main conclusions as follows:The distribution characteristics of monthly dustfall were disclosed in the scale of month ,season and year respectively, it is showed that interannual variation had an obvious falling trend ,which was further divided into three stages of rising ,falling and even period, that dustfall was higher in the seasons of spring and summer while lower in winter and autumn,with a monthly distribution of two high in April and July, and two low in June and October, due to meteorological reason. Analysis of wavelet found that the cycle of three months,one year, quasi-two years and quasi-18 years is obvious. Discontinuity characteristic of dustfall was found by means of analysis of self-correlation ,probabally is a reflection of effective environmental management and change of dust source.More important,the relationships between dustfall and meteorological factors were explored, it was found that the frequency of southern wind direction and high wind velocity, rainfall or rain days play a significant role in the quantity of monthly dust fall, and that the role of relative humidity and temperature might be negligible. Meanwhile, the meterological contribution mechanic and interpretation of monthly dustfall variation were gived in brevity. The role of wind direction is blowing dust particles downward,wind velocity blowing dust particles into sky,and rainfall washing dust particles from sky or weting ground.Quantitative relationship between dustfall and meterological factors was established by means of stepwise regression.the equation is not only significant in statistics,but also has a estimating capability ,which was testified by new data.This implied that it is feasible to forecast dustfall on the basis of meterological factors.Synoptic background patterns of dust deposition were classified into A,B,C,D and E,which is different in dustfall ,by method of clustering.Pattern A has the highest amount of dustfall.The sliding correlation patterns were explored . It was found that the quantity of monthly dustfall was significantly correlated with frequency of southern wind direction, which was varied with time going, that the correlation mode was characterised by piecewise continuity,that the ditnbution of positive coefficient showed a shift from south towards east, and that probabaly there is a weakening relationships between wind direction and dustfall in Shanghai, which probabaly was a reflection of environmental management.