“…Examples include time-series analyses using linear and nonlinear regression techniques (Buda and DeWalle, 2002;Seto et al, 2002;Nickerson and Madsen, 2005), cluster and principalcomponent analyses (e.g. Dorling et al, 1992;Cana-Cascalar, 2002), and spatial-pattern analyses of atmospheric circulation (Davies et al, 1991;Yarnal, 1991Yarnal, , 1993Dorling et al, 1992;Lamb, 2003, 2005). Typical studies employ the ionic concentrations, rather than the deposition flux itself, because precipitation composition is closely linked to the concentrations of precursors in air (Engelman, 1971;Davis et al, 1997;Hicks, 2005).…”