Abstract
Based on the grid-nesting method proposed by the present author (1974), a Movable, multi-Nested Grid scheme (hereafter, MNG) is formulated to apply to a three-level primitive equation model in the σ-coordinate system. The outermost grid size is 381km at 6°N and the mesh ratio for each inner subdomain is one half. The interface condition between different nets is the so called “two-way” interaction. The Euler-backward scheme is adopted for the time integration. The heating due to cumulus ensemble is represented in the same way as the circular symmetric heating function proposed by Harrison (1973).
Several preliminary tests have been carried out to examine the computational characteristics of the scheme and to see how the present MNG method works with real data (T7609, T7617, T7709 and T7711) produced by the JMA operational objective analysis system. The grid values of the finer grid net are calculated by a cubic interpolation formula step by step, and analyzed values on the innermost grid are modified as a results of the superposition of the symmetric model typhoon which is specified by the observed diameter of typhoon, the central surface pressure, the maximum surface wind and the temperature anomaly.
The scheme has been tested with the 3- and 4-step MNG's. The predicted trajectories of the typhoon with these MNG's show the trend of improvement compared with those obtained by the JMA operational numerical weather prediction models. In addition, the three-dimensional structure simulated by the proposed 4-step MNG scheme is also discussed.
