Transcript 支配方程式

A Next-Generation Atmospheric General
Circulation Modeling
Frontier Research Center for Global Change
Hirofumi TOMITA
Masaki SATOH
Tomoe NASUNO
Shi-ichi IGA
Hiroaki MIURA
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)
 Target resolutions
 5 km or less in the horizontal direction
 Several 100 m in the vertical
 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.
Current Status of Our Model
Model name : NICAM(Nonhydrostatic Icosahedral Atmospheric 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 parameterization
Almost completed ( turbulence, radiation, cloud
physics, surface flux )
 Computational tuning
Vectorization
Well tuned for NEC SX6 architecture
Parallelization
2D decompostion,
Flexible configuration against load imbalance
Target machine
WS-cluster, Linux-cluster, Earth Simulator
Grid Generation Method
(0) grid division level 0
(1) grid division level 1
 Grid generation
(2) grid division level 2
(3) grid division level 3
1. Start from the spherical
icosahedron.
(glevel-0)
2. Connection of the midpoints 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.
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
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
Analized term
Spin-up time NICAM
0 day
60 day
14km grid
model
90 day
30days
Interpolation
7km grid
model
30days
Interpolation
3.5km grid
model
10days
Initial condition： appropriate climatology
of a conventional ＧＣＭ
( CCSR/NIES/FRCGC AGCM ver 5.7)
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 60-90 day
A typical Super Cloud Cluster
Super cloud cluster : ~1000km
Westerly wind burst
Cloud cluster :~100km
Convectively-Coupled Kelvin Wave
High pressure
Low pressure
Hovmoller diagrams of OLR ( 2S-2N )
NICAM-14km
NICAM-7km
 Westward moving of CC
 Lifetime of 2days
 Eastward propagation of SCC
NICAM-14km:
20~25 days
 fast propagation
NICAM-7km, 3.5km :
25-40 days
 corresponding to MJO
 also well organized
rather than NICAM-14km.
NICAM-3.5km
Histograms of diurnal cycle for precipitation
Peak : midnight
Peak : early morning
LT [hr]
 Consistent with the obs.
in open ocean
LT [hr]
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 :
–
120km  12km
Reduction of earth radius : 1/10
1.2km grid interval