Studies On The Forecast Of SO₂ Concentration In Xi'an City

The forecast of SO² concentration in Xi'an city had been studied according to the SO² concentration value that monitored from June 2000 to March 2005 and the ground meteorological data from June 2001 to March 2005 of Xi'an city.Results on the analyse of characters of SO² Concentration in Xi'an city indicated that: average annual SO² concentration descended year by year from 2001 to 2003, while the concentration in 2004 rised abruptly; every season concentration descended firstly and then rised greatly; the change of month concentration is like a anisomerous W; the concentration in heating season is doubled that in unheating season; the change of month concentration in every year of monitoring points was in consonance with that of in Xi'an city; the carve of xiaozhai changed violently, and that of xingqingxiaoqu changed flatly.Beacause there is a close correlativity between SO² concentration and meteorological condition, the changes of meteorological condition was analyzed firstly. Then statistical analysis had been done with the meteorological data in the days (API>50). On the basis of contrast, confirm possible meteorological condition that can arise SO² concentration.The dissertation chooses stepwise regression analysis and main element regression in the excessive-member statistical method to build forecast model in the heating and unheating seasons. REG process in the SAS system had been used to eliminate the total line in the stepwise regression analysis. Main element regression combines together main element analysis and regression analysis; it overcomes the difficulty of the highly relevance between the independent and dependent variables. Through checkout, the veracity of model built by stepwise regression achieved 87.09% and 79.75%, the class veracity achied 100%; the veracity of model built by main element regression achieved 67.16% and 56.34%, the class veracity achied 100%. After contrast them, stepwise regression analysis is more accurate.In addition, direct against the current situation of Xi'an city, the paper proposed some suggestions from such respects as the engineering, environmental management, economic decision, city afforestation and soon. Have emphasized it on the thinking of regional integrated control of " putting prevention first ", and have offered certain reference for the integrated control of the SO₂ pollution in Xi'an city.