SPATIAL VARIABILITY OF SYDNEY AIR-QUALITY BY CUMULATIVE SEMIVARIOGRAM

This paper establishes that an isotropic spatial correlation function in the form of a modified Bessel function of the second kind, first or der, can be used to model the spatial variability of a pollution conce ntration held over a sufficiently long period of time in which the var iability due to meteorological factors has been smoothed out. The corr esponding cumulative semivariogram is derived and fitted by nonlinear least-squares to monthly averaged ozone data at 18 monitoring stations of the Sydney region. The good fit of the model indicates that the Sy dney airshed has homogeneous and isotropic subregions whose radius of influence is about 17 km. The Bessel function form of the spatial corr elation has a physical meaning as it is derived from the diffusion equ ation; hence, it is expected that the model can be used, in general, t o represent the spatial variability of a smoothed homogeneous and isot ropic concentration held. (C) 1997 Elsevier Science Ltd.