Important tracer tendency terms in Equation (8) for a short-lived tracer (upper panel, τ_c = 10⁷ s) and a long-lived tracer (lower panel, τ_c = 10¹⁰ s) in Experiments I. The black lines represent the term ﹩w\tfrac{\partial \overline{\chi }}{\partial z}﹩ and the red are ﹩{e}^{z}\tfrac{\partial }{\partial z}[{e}^{-z}(w{\chi }^{{\prime} }-\overline{w{\chi }^{{\prime} }})]﹩.