A Modified Upstream Differencing Technique for Solving the Advection Equation

摘要

A scheme for numerical modelling of advection of meteorological parameters has been developed and is now used in operational models of the AFGWC. In this scheme, new values are determined at each time step for each grid point of the prediction matrix by first determining the upstream trajectory position at the previous time step and the corresponding parametric values, and then modifying the grid point values. This quasi-Lagrangian advection scheme, which is inherently computationally stable, allows use of any reasonable time step and almost total elimination of artificial smoothing. This technique effects preservation of tight gradients and flow patterns with minimal distortion through the forecast period, as well as more realistic movement and retention of extreme parametric values of analyzed features. (Author)