The EVAD technique,which was presented by Srivastava,is often unsolvable because there usually exists sick matrix in practice.Thomas utilized the weighting function method to solve the problem.In this article,a modified Gram-Schmidt arithmetic(MGS) is introduced to solve the same problem.The atmospheric mean horizonal convergence in two examples is calculated using the two modified EVAD methods,the convergence obtained is then adjusted with the variational method,and the vertical velocity is computed in terms of the continuity equation.At last,various computed results are compared and analyzed.