Frontier Research Center for Global Change Hirofumi TOMITA Masaki SATOH Tomoe NASUNO Shi-ichi IGA Hiroaki MIURA Hirofumi TOMITA Masaki SATOH Tomoe NASUNO Shi-ichi IGA Hiroaki MIURA A Next-Generation Atmospheric General Circulation Modeling

Contents Motivation of our new modeling Global cloud resolving model To avoid the ambiguity of cumulus parameterization Model description Quasi-uniform grid in the horizontal direction Icosahedral grid Nonhydrostatic framework Suitable for climate simulation Aqua Planet Experiment The first attempt of global cloud resolving in a long term Summary and Future plan

Motivation (1) General problem for current AGCMs Cumulus parameterization One of ambiguous factors Statistical closure of cumulus convections Future AGCM Explicit treatment of each cloud Cumulus parameterization Large scale condensation scheme : not used! Cloud microphysics : used! Explicit treatment of multi-scale interactions Each cloud scale  meso-scale  planetary scale  Global Cloud Resolving Model

Motivation (2) Strategy of dycore development Quasi-uniform grid Spectral method : not efficient in high resolution simulations. –Legendre transformation –Massive data transfer between computer nodes Latitude-longitude grid : the pole problem. –Severe limitation of time interval by the CFL condition. The icosahedral grid: homogeneous grid over the sphere –To avoid the pole problem. Non-hydrostatic equations system Very high resolution in horizontal direction. Target resolutions 5 km or less in the horizontal direction Several 100 m in the vertical

Current Status of Our Model Model feature Governing equations Full compressible non-hydrostatic system  including acoustic wave Spatial discretization Horizontal grid configuration Vertical grid configuration Topography Finite Volume Method Icosahedral grid Lorenz grid Terrain-following coordinate Conservation Total mass, total energy Temporal scheme Slow mode － explicit scheme （ RK2 ） Fast mode － Horizontal Explicit Vertical Implicit scheme （ HEVI ) Physical parameterizationAlmost completed ( turbulence, radiation, cloud physics, surface flux ) Computational tuning VectorizationWell tuned for NEC SX6 architecture Parallelization2D decompostion, Flexible configuration against load imbalance Target machine, Earth Simulator WS-cluster, Linux-cluster, Earth Simulator NICAM( Nonhydrostatic Icosahedral Atmospheric Model ) Model name : NICAM( Nonhydrostatic Icosahedral Atmospheric Model )

Grid Generation Method Grid generation 1.Start from the spherical icosahedron. (glevel-0) 2.Connection of the mid- points of the geodesic arc  4 sub-triangle (glevel-1) 3.Iteration of this process  A finer grid structure (glevel-n) # of gridpoints 11 interations are requried to obtain the 3.5km grid interval. (0) grid division level 0 (1) grid division level 1 (2) grid division level 2 (3) grid division level 3

Aqua-Planet Experiment Past reseaches Hayashi & Sumi (1986), Swinbank et al.(1988) Behaivior of MJO etc. Gotswami et al.(1984), Numaguchi(1995) Formation and intensity of Hadley circulation APE as a standard test case Neale & Hoskins(2001) AMIP-like model intercomparison experimental setup Fixed zonal-symetric SST Prescribed Ozone distribution Equinoctial solar radiation investigate the dependency of cumulus param. on the results to perform theAPE by a cloud resolving model Our approach: to perform the APE by a cloud resolving model  resolution （ 15km ～ 3.5km ） ONE REFERENCE RESULTS against other parameterization models

Series of experiment by NICAM 0 day 60 day Spin-up time NICAM 14km grid model 7km grid model 3.5km grid model Interpolation 30days 90 day Analized term 30days Initial condition ： appropriate climatology of a conventional ＧＣＭ ( CCSR/NIES/FRCGC AGCM ver 5.7) 10days Interpolation

OLR(1S-1S 平均 ) Precipitation rate [mm/day] at day 85 : log-scale by NICAM-3.5km model Super cloud cluster Mid-latitude cyclone

OLR (7km-model) during day

A typical Super Cloud Cluster Cloud cluster :~100km Super cloud cluster : ~1000km High pressure Low pressure Westerly wind burst Convectively-Coupled Kelvin Wave

Hovmoller diagrams of OLR ( 2S-2N ) NICAM-14km NICAM-7km NICAM-3.5km  Westward moving of CC  Lifetime of 2days  Eastward propagation of SCC NICAM-14km: 20~25 days  fast propagation NICAM-7km, 3.5km : days  corresponding to MJO also well organized rather than NICAM-14km.  also well organized rather than NICAM-14km.

Histograms of diurnal cycle for precipitation LT [hr] Peak : midnight Consistent with the obs in open ocean  Consistent with the obs. in open ocean Peak : early morning

Summary We have developed a global CRM in order to avoid the ambiguity on the cumulus parameterization. Nonhydrostatic system Icosahedral grid As the first attempt of GCRM, we performed an Aqua-Planet-Experiment. Hierarchical structure of cloud convections MJO-like signal with realistic phase speed Diurnal cycle of precipitation We confirm that the GCRM approach becomes the one of major approach in the climate research field in the near future. The Global Cloud Resolving Climate Simulation is not a dream!

Example of stretched grid Default grid : glevel-6 120km grid intv. Homogenious Stretched grid After the transformation Grid interval : 12km –120km  12km Reduction of earth radius : 1/10 1.2km grid interval