Hello, I have a daily data set with 240 observations of PM10/m3 (particle matter with diameter smaller tham 10um) concentrations measured in 8 points (for 30 days).
My variogram in time is quite nice (spherical, with 1 structure of 7 days). very good fitting. My variogram in space is fitted using a standardized variable, which means that each value z(s,t) in moment t in point s, is transformed in z(s,t)*=[z(s,t)-m(s)]/s(s) where: m(s) is the mean of the 30 days array in point s; s(s) is standard error of the 30 days array in point s. In this case the variogram also fits very nice, but it doesnt reach the sill (my argument to explain this is because most of the varibility is in time domain, not in space domain), and so i have a zonal anisotropy. After transforming anisotropic model in an isotropic model, i wanted to create several realizations of my spatio-temporal process using Sequential Gaussian Simulation (SGS). However i wanted to use my original values z(s,t) (which didn't show any spatial structured phenomenom), instead of z*(s,t). The result is a dramatic variogram where my range and variance aren't reproduced. I would like to know if anybody can help me understanding the problem and how to correct it. Thanks, Manel
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