Deviation of log ξ (a) and the dispersion of the Fe ion concentration (b) plotted as a function of gas densities for light curves with fractional variability ranging from 10% to 50% (the simulated light curve shown in Fig. 1 has an average fractional variability, F_var, of ∼40%). The deviation of log ξ is calculated as the difference between the intrinsic value and the value obtained from a single equilibrium component fitting of the simulated Fe ion concentration distribution, such as the ones shown in Fig. 2. The curves representing the averages over the nine warm absorber components (see Table 1) are plotted for both the deviation and dispersion.