THE FORECASTING OF ATMOSPHERIC POLLUTANT DENSITY IN XI'AN CITY

Wang Fanqiang

(Shaanxi Meteorological Office, Institute of Meteorological Science, Xi'an 710015, PR China)

Abstract

Based on the observed daily data of three main pollutants (PM₁₀, SO₂, NO₂) and metrological data from January 2001 to December 2003 of Xian City, the spatial and temporal distributions and variations of the pollutant densities were analyzed. By using the radiosonde and surface observation data of Xian, 11 surface meteorological elements and 9 atmospheric stratification parameters which affect the density of atmospheric pollutant were calculated. A series of regression equations for every month were built with them and the density of PM10, SO₂, and NO_x between 2001 and 2003. The regression equations of July as follow (unit: ug/m³):

21.62-0.34X₁-0.20X₂+1.30X₃-0.99°Á10^-3X₁₂+1.75°Á10^-3X₁₆

51.81-0.20X₄-0.195X₅-0.917X₁+0.391X₆ -1.375°Á10^-3X₁₂+1.22°Á10^-3X₁₃-

2.705X₁₄+0.635°Á10^-3X₁₅+1.76°Á10^-3X₁₆

182.5-1.01X₇-1.701X₄-1.170X₅-0.276X₈+2.135X₉-60.0X₁₆-1.695°Á10^-3X₂₀

Where X₁ is the daily minimum temperature(°æ), X₂ is the pressure variation of 24h at surface(hpa), X₃ is the atmospheric stability, X₄ is the value of low cloud, X₅ is the visibility(km), X₆ and X₇ are the daily mean temperature, the dew-point temperature(°æ), X₈ is the daily rain( mm), X₉ is the daily maximum temperature minus the daily minimum temperature, X₁₂ and X₁₃ are the maximum and minimum mixing condensation levels(m), X₁₄ is the height of inversion base(m), X₁₅ and X₁₆ are the thick and the intensity of inversion layer(m, °æ/100m), X₂₀ is the ventilation coefficient, (m²/s).

With the application of daily numerical prediction and local weather forecast, by using the program of VB6.0, an operation system is established for air pollutant density in Xian City, and then pollutant densities are used to predict from February 2004, the forecast show that the results as well.

Keywords: air pollutant, density, Forecasting.