Empirical Orthogonal Function models

Finnigan and Shaw [188] conducted an Empirical Orthogonal Function (EOF) analysis of an extensive wind tunnel data set obtained in a model wheat canopy. The same authors have recently performed an equivalent analysis based upon the output from the large-eddy simulation described above. 

Receptor models can also be used together with spatial distribution of measurements to estimate the spatial distribution of emission fluxes. The empirical orthogonal function (EOF) method is one of the most popular models for this. Henry et al. (1991) improved the EOF method by using wind direction in addition to spatially distributed concentration measurements as input. We describe this approach below. 

RECEPTOR MODELING METHODS 1263 24.1.3 Empirical Orthogonal Function Receptor Models... 

Peterson used the skill score to evaluate the performance of his empirical statistical model based on orthogonal functions. The skill score equals 1.0 when all calculated and observed concentrations agree, but 0 when the number of correctly predicted results equals that expected by chance occurrences. The statistical technique had a skill score of 0.304. An 89-day, 40-station set of the data was used to check a Gaussian diffusion model, and this technique gave the diffusion model a skill score of only 0.15. (Recall that the statistical empirical model was used for 24-h averaged sulfur dioxide concentrations at 40 sites in St. Louis for the winder of 1964-1965.)... 

Population analysis in semiempirical methods fall into two categories. Methods including overlap in the Fock equations use the Mulliken population analysis. The majority of semiempirical methods uses the ZDO approximation, and the net charges are interpreted on the basis of symmetrically orthog-onalized AOs. It is pointed out that this interpretation is not exactly valid, because of truncation and empirical adjustment. But the corresponding nonsymmetrical orthogonalization is not uniquely defined. Charge models based on semiempirical wave functions play an important role in the calculation of molecular electrostatic potentials for reactivity. 

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