**6. References**


Maloney and Hartmann, 2001)? Or do we need further increase in the model resolution (Hayashi and Golder, 1986; Gualdi et al., 1997; Grabowski and Moncrieff, 2001; Inness et al., 2001; Liess and Bengtsson, 2004)? The use the Betts-Miller-Janjic (Janjic, 1994) scheme did not improve the MJO simulation. Similarly, higher resolution nested domains inside the NRCM made minor differences. Further works need to be done to investigate the roles of

The lack of MJO in the NRCM does not necessarily imply a lack of tropical-extratropical interaction. For example, if the observed source of perturbations that eventually initiate an MJO event is located inside the model domain, then the lateral boundary conditions may not be effective beyond the MJO predictability limit. As a result, the locations of the meridional boundaries of the NRCM are crucial for capturing the extratropical influences, if

The NRCM is an atmosphere only model forced by the SST without true oceanic feedback. Therefore, it is difficult to rule out the role of coupled air-sea feedbacks in modulating the mean state (Hendon, 2000; Zheng et al. 2004; Vitart et al. 2007; Woolnough et al. 2007). Pegion and Kirtman (2008a, b) found that air-sea coupling was responsible for differences in the simulation of the MJO between the coupled and uncoupled models, specifically in terms of organization and propagation in the western Pacific. The role of intraseasonally varying SST was found to be important to the amplitude and propagation of the oscillation beyond the Maritime continent in their model. After removing the intraseasonally varying component in the SST and lateral boundary conditions in MM5, Gustafson and Weare (2004b) found only minor differences in the MJO simulation compared to the simulation forced with observed SST. Ray et al. (2009) also reported that use of constant SST did not influence the MJO initiation in the Indian Ocean. These results indicate that the MJO amplitude and propagation are influenced by the air-sea interactions whose effect is

In short, we have shown that the erroneous mean state may be responsible for poor MJO simulation in the model. Our results call for further research attention towards using the

Acknowledgment is made to the NCAR, which is sponsored by the National Science Foundation, for making the NRCM model output available. The NCEP-NCAR reanalysis

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dominant over the Pacific.

**5. Acknowledgment** 

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**5** 

Kazuo Saito

*Japan* 

*Meteorological Research Institute* 

**The JMA Nonhydrostatic Model and Its** 

**Applications to Operation and Research** 

Nonhydrostatic models were initially developed as research tools for small scale meteorological phenomena. Today, several nonhydrostatic models have been developed and applied to numerical simulations and operational numerical weather prediction (NWP). In this chapter, we review the Japan Meteorological Agency (JMA) nonhydrostatic model (JMA-NHM, hereafter referred to as NHM) and its applications to operational forecasts and research fields. Section 2 presents a brief history of the model development from a research tool to a full-scale NWP model. In section 3, we review applications of the model to several research fields of various time/spatial scales from tornado to regional climate modelling, and mesoscale data assimilation and ensemble prediction studies. Section 4 introduces on-

going relevant topics including the Japanese next generation supercomputer project.

Following Gal-Chen and Somerville (1975), the terrain-following vertical coordinates

*z*

1 1 \* \* 1 <sup>13</sup> <sup>23</sup> 2 2 <sup>2</sup> 1 , ( 1) , ( 1) , *sss zzz z z <sup>G</sup> G G G G H Hx Hy* 

and the metric tensors for the coordinate transformations were employed:

where *zs* is the surface height and *H* is the model top height.

The JMA nonhydrostatic model (NHM) was first developed as a research tool at the Meteorological Research Institute (MRI). Ikawa (1988) developed a nonhydrostatic model with orography and compared computational schemes with a 2-dimensional numerical experiment.

\* ( ) , *<sup>s</sup>*

*Hz z*

*H z*

The first version of NHM used the anelastic (AE) scheme to solve the Navier-Stokes momentum equations for a fluid. The AE model removes sound waves from solutions in the

*s*

(2)

(1)

 

> 

**1. Introduction** 

**2. The JMA nonhydrostatic model** 

**2.1 Development of NHM at MRI** 

**2.1.1 Anelastic equation model** 

