Frontier Research Center for Global ChangeFrontier Research Center for Global Change Hirofumi TOMITAHirofumi TOMITA Masaki SATOH Masaki SATOH Tomoe NASUNO Tomoe NASUNO Shi-ichi IGA Shi-ichi IGA Hiroaki MIURA Hiroaki MIURA

A Cloud-Resolving Aqua Planet ExperimentA Cloud-Resolving Aqua Planet Experiment

ContentsContents

Brief introduction of our model Global cloud resolving model

• To avoid the ambiguity of cumulus parameterization

New framework for AGCM• Icosahedral grid

• non-hydrostatic dynamics

Aqua Planet Experiment --- control run Method of expermental setup for high-resolution GCRM

• Spin-up

• Model setup

Results• Tropical variability

• Resolution dependency

Summary

Brief introduction of our model devlopment(1)Brief introduction of our model devlopment(1)

Many variations in the tropical feature in the AGCMs

Wave propagation• Eastward / Westward?• Dominant wavenumber?

Results depend on cumulus parameterization.

General concerning issue for current AGCMs

Cumulus parameterization• One of ambiguous factors• Statistical closure of cumulu

s convections

Hovmeller diagram for precipitation on the tropics

Produced by Dr. Williamson

Brief introduction of our model development(2)Brief introduction of our model development(2)

Avoid the uncertainties owing to cumulus parameterization Super-parameterization ( Grabowski 2001 )

• Embed a 2D CRM into the each of grid box

• Interact with large-scale motion in the AGCM.

• However, problems as follows.– How is 2D-CRM configurated in the grid box?– Scale-separation between the 2D-CRM and the host AGCMs.

Global cloud resolving ( our approach )• Explicit treatment of each cloud

– Cumulus parameterization

Large scale condensation scheme : not needed!– Cloud microphysics : used!

• Direct treatment of multi-scale interactions– Each cloud scale meso-scale planetary scale

Brief introduction of our model development (3)Brief introduction of our model development (3)

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 NICAMCurrent Status of NICAM

Model feature

Governing equations Full compressible non-hydrostatic systemFull compressible non-hydrostatic system

　　　 including acoustic wave

Spatial discretization

Horizontal grid configuration

Vertical grid configuration

Topography

Finite Volume Method

Icosahedral gridIcosahedral grid

Lorenz grid

Terrain-following coordinate

Conservation Total mass, total energyTotal mass, total energy

Temporal scheme Slow mode 　－　 explicit scheme 　（ RK2 ）Fast mode －　 Horizontal Explicit Vertical Implicit 　　　　　　　　　　　 scheme （ HEVI )

Physical parameterization 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

Model name : NICAM(NICAM(Nonhydrostatic Icosahedral Atmospheric ModelNonhydrostatic Icosahedral Atmospheric Model))

Method (1)Method (1)

Experimental setup follow the CONTROL RUN of Neal & Hoskins(2000)

• SST distribution / ozone distribution

Difficult to perform the 3.5 years by GCRM.• Owing to computational limitation

• Several months integration starting an appropriate climatology

Spin up Initial condition

• 3.5 year integration by CCSR/NIES/FRCGC AGCM ver.5.7 with T42L59.

• 3 years climatology as an initial condition.

• Interpolate to NICAM gridpoints.

Method (2)Method (2)

NICAM Model setup Horizontal resolution : 14km, 7km, 3.5km Vertical layer : 54 layers

• 75 m at the lowest layer• 750 m in the upper troposphere

Time step : 30sec(14km, 7km), 15sec(3.5km) Cloud microphysics

• Globowski(1998) scheme– Including simple ice phase effects

• All the runs employ the same microphysics– To isolate the impact of resolution

Turbulence : Mellor & Yamada level 2 Surface flux scheme : Louis(1979) scheme Radiation scheme : Nakajima et al.(2000) scheme Rayleigh damping

• z>25km : reduce the reflection of gravity waves.

Series of experiment by NICAMSeries of experiment by NICAM

0 day 60 day

Spin-up time NICAM

14km gridmodel

7km gridmodel

3.5km gridmodel

Interpolation

30days

90 day

Analized term

30days

Initial condition ： appropriate climatology of a conventional ＧＣＭ ( CCSR/NIES/FRCGC AGCM ver 5.7)

10days

Interpolation

Reach an equilibrium state?Reach an equilibrium state?

First 60 days:Spin-up time by

14km model

First 30 days:These values change.Broclinic waves are developing.

Second 30 days:Broclinic wave well developes.Reach an equilibrium state

Last 30 days :Analyzed term Well stable.

OLR(1S-1SOLR(1S-1S 平均平均 ))Precipitation rate [mm/day] at day 85 : log-scaleby NICAM-3.5km model

Super cloud cluster

Mid-latitude cyclone

Propagation of convective regionPropagation of convective region

Produced by Dr. Williamson

2 or 3 convective regions Eastward propagation with 30-days period One strong convective region

Hovmeller diagram for precipitation on the tropics

westward

eastward

CRM-results: NICAM

Comparison with observation (1)Comparison with observation (1)

Takayabu et al., 2000

SST distribution on May 1998

El Nino season : Contrast between warm pool & cold pool is weak. similar situation to CNTRL RUN.

Hovmellor of precipitation

• One strong SCC: One strong SCC: eastward propagation eastward propagation

around the globearound the globe

30days period30days period

Investigation of MJO in El Nino

Comparison with observation (2)Comparison with observation (2)

Observation result CRM result : NICAM

Simlar feature:One strong SCCPeirod of 30days

Hovmoller diagram (dx=7km) 1N-1SHovmoller diagram (dx=7km) 1N-1S

90d

80d

60d

90d

80d

60d

OLR Temperature (tropospheric mean)

Zonal Velocity (z=10m) Surface pressure

LL

HH

WW

CCWave number 1 structure

AA

AABB

CC

In the wavenumber 1 structure,there are several convective regions.

Vertical structure at day 80 (dx=7km)Vertical structure at day 80 (dx=7km)

A BA B

Cool Warm CoolCool Warm Cool

Wavenumber 1

Diabatic heating / boomerang shape

Vertical structure at day 83 (dx=7km)Vertical structure at day 83 (dx=7km)

A B CA B C

Cool WarmCool Warm

Strong vertical shear

rear inflow

Squall line

cloud top : high

cloud top : low

A typical Super Cloud Cluster (1)A typical Super Cloud Cluster (1)

Cloud cluster :~100km

Super cloud cluster : ~1000km

High pressure Low pressure

Westerly wind burst

Convectively-Coupled Kelvin Wave

A typical Super Cloud Cluster (2)A typical Super Cloud Cluster (2)

Zonal elongation as two lines off the equator Splitting of convection area within SCC

OLR (7km-model) during 60-90 dayOLR (7km-model) during 60-90 day

Super Cloud Cluster and Cloud ClusterSuper Cloud Cluster and Cloud Cluster

Eastward propagationof SCC

a

a

a

a

b c

b

b

b

c

c

c

d

d

Westward propagation of CC

Meso-scale cloud system Meso-scale cloud system

a bc

Meso-scale cloud system : ~ 10km

Northeasterly

Wind at SFC.

Convergence line:South-edge of CC

Each of MCS has cold pool Cold pool dyanmics

Liquid water path Temperature at the surface

Resolution dependency of propagation waveResolution dependency of propagation wave

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 : 25-40 days like MJO also well organized also well organized rather than NICAM-14km. rather than NICAM-14km.

Hovmellor diagram of OLR ( 2S-2N )

Resolution dependency of ITCZResolution dependency of ITCZ Mass-weighted T & precip. water

little difference

Precipitation significant difference As resolution increases,

• Precipitation decreases on the equator.

• ITCZ region is elongated in the latitudinal.

For the coarser resolution,• Cloud condensation hardly oc

curs at the sub-tropics when trade-wind converges toward the equator.

feature of low-resolution CRM the strong convergence of wat

er vapor on the equator.

Zonal averaged field

Single ITCZ, though splitting convective region within SCC sometime occurs.SCC moves in the latitudinal direction In the non-SCC region, preciptation occurs just on the equator.

Histograms of diurnal cycle for precipitationHistograms of diurnal cycle for precipitation

LT [hr] LT [hr]

Peak : midnight

Consistent with the obsConsistent with the obs. in open oceanin open ocean

Peak : early morning

SummarySummary

We have performed the control run of APE by a global cloud-resolving model. Resolution : 14km, 7km, 3.5km

Hierarchical structure of cloud field can be well captured. MJO-like wavenumber 1 structure Eastward propagation of several super cloud clusters of ~1000k

m with 30-days period. Westward propagation of cloud clusters of ~100km with the lifeti

me of 2days Meso-scale cloud system of ~10km with the lifetime of several ho

urs. Resolution dependency is found at ITCZ in CRM.

As resolution increases, its intensity is smaller and its width is larger.

Cloud resolving model has the reasonable diurnal cycle of precipitation rate at the tropics. Its primary peak is at the early morning, consistent with observati

ons.