Long-term Integration Study Of The Dynamical And Physical Processes Of The GRAPES Non-hydrostatic Model On Yin-Yang Grid

With the rapid advancement of computer capabilities in recent years,the improved high resolution global models are of glowing interest.The GRAPES global system is a fully compressible,non-hydrostatic model with a semi-implicit semi-Lagrangian(SISL)dynamical core developed on the latitude-longitude(lat-lon)grid.However,the pole problem of lat-lon grid brings GRAPES a large computational burden when performing high-resolution calculations.To avoid the pole problem,GRAPES global model is developed on a quasi-uniform Yin Yang grid in this paper(GRAPES_YY).The SISL dynamical core on the Yin Yang grid is coupled with the physical parameterization package of the operational version of GRAPES.In addition,a mass fixer and a fourth-order horizontal divergence damping is added when solving the dynamical core.The long-term integration of Aqua Planet experiment and the five-day simulation for the real case indicate the reasonability and stability of this model.The main conclusions are summarized as follows:The sub-grid physical parameterizations include the RRTMG long-and shortwave radiative transfer model,the MRF planetary boundary layer(PBL)turbulent diffusion,the NSAS shallow and deep convection scheme,the two-moment mixed-phase cloud microphysics scheme,and the CoLM land model.In order to conserve mass in the long-term integration,a fixer is added when solving the equation of ?.A series of explicit horizontal diffusion mechanisms are compared for dissipating spurious high-frequency waves.Numerical tests indicate that the fourth-order horizontal divergence damping eliminate numerical noise the most effectively in GRAPES_YY 1°×1° simulations.3.5-year aqua planet integrations(1°×1°)under three different sea surface temperature conditions(CONTROL,QOBS,and FLAT)are carried out to assess the numerical performance of GRAPES_YY relative to other models.The CONTROL and QOBS show tropical precipitation bands moving eastward with some envelopes of westward convective-scale disturbance.Less organized westward-propagating rainfall cells and bands were seen in the FLAT and the propagation of the tropical wave varied with the SST gradient.The Inter Tropical Convergence Zone(ITCZ),Hadley circulation and westerly jet core weak and shift poleward as the SST profile flat from the CONTROL to the FLAT.The climatological structures simulated by GRAPES_YY generally fall within the bounds of the results from other models.The stronger ITCZ precipitation than other models,accompanied with stronger Hadley cells and convective heating may stem from the contribution of parameterized convection and the non-hydrostatic effects in GRAPES_YY.The NSAS convection scheme tends to make cumulus convection stronger and deeper to suppress the excessive grid-scale precipitation.In addition,the non-hydrostatic dynamical mechanism in the tropics should not be ignored since the strong convection and vertical velocity can be found in the aqua planet CONTROL and QOBS runs.A five-day simulation at 1°×1° resolution for the real case is performed to show the model performances on the prediction of global rainfall and general circulation.The distribution of precipitation and troughs are generally consistent with the reanalysis data.The simulation of real atmosphere,accompanied with the Aqua Planet experiments,confirms that the Yin-Yang gird model can serve as a new version of GRAPES operational tool because of its potential on high resolution improvements.