Preliminary Test of Typhoon Forecast with a Moving Multi-Nested Grid (MNG)

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 a-coordinate system. The outermost grid size is 381 km 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.

Prediction of a typhoon using a fine-mesh NWP model

“…The initial data, as well as the boundary values, were interpolated from the global grid-point model. These initial data contained errors in amplitude and phase of the initial vortex and no symmetric vortex was superimposed on them, as in the MNG (Ookochi, 1978). Despite that, the higher resolution typhoon, differently from that at lower resolution, was able to deepen the central pressure considerably and follow a track parallel to that observed in the last 48 h of the forecast.…”

“…These vary in the sophistication of their physical parameterization; the operational dynamical models are always nested in larger models because of the need of both high-resolution and large-scale formation. Examples of models which use a movable nested grid are the highly sophisticated Movable Fine Mesh (MFM) model developed at NMC (Hovermale and Livezey, 1977), the Movable Multi-Nested Grid (MNG) developed by the Japanese Meteorological Agency (Ookochi, 1978(Ookochi, , 1983, and the Navy's Nested Tropical Cyclone Model (NTCM) (Harrison, 1981). In these models a high-resolution grid, embedded in a larger coarser grid, moves with the tropical cyclone.…”

Applications of Tropical Cyclone Models

“…These further tests over data-sparse oceans, together with the different physics represented by typhoon circulations, will provide additional information regarding the applicability of these fine mesh models. The last model listed in Table 1 is the Japanese Meteorological Agency (J MA) movable multiplynested grid (MNG) developed by Ookochi (1978). This model has been tested on a few typhoons approaching Japan.…”

The Performance of a Typhoon Track Prediction Model with Cumulus Parameterization

“…This difficulty may be due to insufficient model resolution, parameterization for physics, initial condition and so on. Due to limited computer resources, JMA has been operating a special model with a movable multi-nested grid (MNG) developed by Ookochi (1978) for the typhoon track prediction. The MNG model uses a prescribed heat source with an axisymmetric structure for cumulus convective process.…”