Abstract:
Several kinds of typical height-based terrain-following coordinates, such as the Gal Chen&Somerville coordinate (hereafter “Gal.C.S”coordinate), the smoothed level vertical coordinate (hereafter SLEVE coordinate) and a new coordinate called as the cosine-smoothed coordinate (hereafter“COS”coordinate), were theoretically analyzed and intercompared with each other via the induced errors by calculations of the PGF (Pressure Gradient Force) and the 2D-ADV (2-dimensional mass advection) tests. The results of calculation of the PGF showed that the errors of the calculation of the PGF induced by using a terrain following coordinates, were significantly decreased by using SLEVE1, SLEVE2 and COS coordinates in comparison to the Gal.C.S coordinate.SLEVE2 and COS coordinates were relatively better in reduction of the errors of the PGF calculation. The decaying coefficient “b” and its Jocabian derivative played a deterministic role in reduction of the errors. The similar remarks could be made for the tests of the 2D-ADV calculation. The errors of the 2D-ADV calculation by using the COS coordinate were the smallest as compared with those of the reference test in which there were no terrain. The COS coordinate was most advantageous among all the four coordinates in tests.