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EVALUATION OF ACID DEPOSITION MODELS USING PRINCIPAL COMPONENT SPACES
Citation:
Cohn, R. AND R. Dennis. EVALUATION OF ACID DEPOSITION MODELS USING PRINCIPAL COMPONENT SPACES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/450.
Description:
An analytical technique involving principal components analysis is proposed for use in the evaluation of acid deposition models. elationships among model predictions are compared to those among measured data, rather than the more common one-to-one comparison of predictions to measurements. ultidimensional comparison of principal component spaces, using general methodology developed by Krzanowski (1979), is the basis of the technique. he technique is illustrated using concentrations measured by aircraft over the eastern United States. odel predictions are generated by the Regional Acid Deposition Model (RADM). imple example provides motivation for the technique. ore detailed applications are shown for systems of concentrations involved in the creation of sulfur and nitrogen deposition, respectively. rthogonal vectors describing the two-dimensional principal component spaces are calculated for measurements and predictions, such that the angles between measured vector i and predicted vector i (i = 1,2) are minimized. sing one of the two approaches that are presented common scaling factors), the agreement between measured and RADM-predicted spaces is generally good in the sulfur system, with angles of 4.5 degrees and 11.4 degrees. greement is weaker in the nitrogen system (17.2 degrees and 27.7 degrees). ssues of interpretation and potential extensions of the technique's applicability are discussed.