190 Kikuro Miyakoda
Fig. 10.4 Multiply-nested-movable mesh
rnet;hC
1
2 5 8
31 4 617 9P~ I I I
Fig. 10.5. Time integration order of
the MMM model
meridional direction if the mesh center becomes separated from the forecast storm
center by more than one mesh M resolution.
Construction of initial comditions: Initial condition for the MMM model rely on
both the global analysis performed at NCEP and the information on the tropical
cyclone structure prepared at National Hurricane Center, USA. The latter is utilized in generation of the tropical cyclone vortex. A tropical cyclone analyzed in
the NCEP global analysis tends to be too large and too weak. Therefore, the model
initialization method is formulated using a vortex replacement strategy.
Controlled spin-up of a vortex:
In course of time integration which starts from a calm condition, the tangential
wind in the free atmosphere is nudged toward a time dependent reference wind
field. This wind field gradually approaches the target field in a long time scale of
vortex evolution, e.g., 60 hours.
Time integration scheme: At two-step iterative time integration scheme is used,
:t.h = LF+HF+DF+AD
(29)
where h represents a time dependent variable: h=u, v, T, r, (r: the mixing ratio of
water vapor), P. is the pressure at the surface, and LF and HF are the low and high
frequency terms, respectively, DF, the diffusion term and AD the forcing term
Fig. 10.4 Multiply-nested-movable mesh
rnet;hC
1
2 5 8
31 4 617 9P~ I I I
Fig. 10.5. Time integration order of
the MMM model
meridional direction if the mesh center becomes separated from the forecast storm
center by more than one mesh M resolution.
Construction of initial comditions: Initial condition for the MMM model rely on
both the global analysis performed at NCEP and the information on the tropical
cyclone structure prepared at National Hurricane Center, USA. The latter is utilized in generation of the tropical cyclone vortex. A tropical cyclone analyzed in
the NCEP global analysis tends to be too large and too weak. Therefore, the model
initialization method is formulated using a vortex replacement strategy.
Controlled spin-up of a vortex:
In course of time integration which starts from a calm condition, the tangential
wind in the free atmosphere is nudged toward a time dependent reference wind
field. This wind field gradually approaches the target field in a long time scale of
vortex evolution, e.g., 60 hours.
Time integration scheme: At two-step iterative time integration scheme is used,
:t.h = LF+HF+DF+AD
(29)
where h represents a time dependent variable: h=u, v, T, r, (r: the mixing ratio of
water vapor), P. is the pressure at the surface, and LF and HF are the low and high
frequency terms, respectively, DF, the diffusion term and AD the forcing term