“…Many methods have been developed so far for analyzing the stability and convergence of the numerical schemes, including energy method [14], matrix property analysis method [28], and Fourier method [1,4], etc. Among them, the Fourier method is frequently used, especially when performing the numerical stability, see, e.g., [5,31,33] and the references therein. However, the existing literatures using Fourier method to do convergence analysis requires a strong assumption on the truncation error function.…”