Tracer transport simulation
by an icosahedral grid model
Center for Climate System Research, Univ. of
Tokyo
Yosuke Niwa
R. Imasu, M. Satoh, S. Maksyutov,
T. Machida, H. Matsueda
NICAM
Nonhydrostatic ICosahedral Atmospheric Model
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NICAM was first developed by Satoh (CCSR/FRCGC) and H.
Tomita (FRCGC).
(H. Tomita and M. Satoh, 2004, M. Satoh et al., 2007)
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Developed as a global cloud resolving model (GCRM).
The max resolution… dx~3.5km
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NICAM is also used as a low-resolution Atmospheric
Circulation Model (AGCM) and as a regional model (StretchNICAM).
I used NICAM as a AGCM and modified it an on-line tracer
transport model.
I added new tracers and developed nudging module
resolution…dx~240km
Realistic
experiment by
NICAM
A 3.5km-mesh global
simulation was
performed using the
Earth Simulator.
(H. Miura et al., 2007)
dx~3.5km
OLR (by H. Miura)
http://www.ccsr.u-tokyo.ac.jp/~satoh/nicam/index.html
Grids of NICAM
Horizontal grid:
Regional model version:
recursively divided
icosahedral grid
stretched grid
Vertical grid:
Terrain-following coordinate:
zT ( z  zs )
z* 
zT  zs
z*
zT : top of model domain
z s : surface height (depends on horizontal location)
z : height above sea level
It looks like σ coordinate, but doesn’t depends on
pressures and is not time-variable.
Advantages of NICAM for tracer transport
simulations
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High-resolution
if I could use the Earth Simulator
Tracer masses are completely conserved without a mass fixer
Tracer advection is consistent with continuity
Easy to develop adjoint code
no limiters or fixers, not semi-Lagrangian scheme
→ good properties for high-resolving inverse method.
Since NICAM is a new model, evaluation of the model
performance is needed.
The setting of NICAM
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Horizontal resolution: dx~240km
The number of vertical layers: 54
Time step: 20 min
Advection scheme : Miura2004 scheme (horizontal)
2nd order difference (vertical)
Cumulus convection : simplified prognostic Arakawa- Schubert
Vertical diffusion : Mellor-Yamada 2 with modification by Smith (Smith, 1990)
Analysed fields used for nudging: NCEP, JRA (not submitted to TC cont.)
Meteorological variables used for nudging: U , V (τ=0.7day), T (τ=3day)
Nudged only for the free troposphere (12th layer ~)
not nudged in boundary layers
Evaluation of meridional transport
comparison with TransCom 3 models ①
tracer : fossil fuel 1990
Surface
500hPa
The North-South gradient simulated by NICAM is smaller than
other models.
Evaluation of meridional transport
comparison with TransCom 3 models ②
tracer : fossil fuel 1990
stronger inter-hemispheric transport
NICAM
TransCom 3 models
CTL
sub-grid transport by cumulus
convection was reduced by half
dynamical field simulated by
NICAM is not problem
Nudged
½ cumulus effect
cumulus
convection
hardly affect!
Large scale advection is the cause of inter-hemispheric transport
Due to the advection scheme of NICAM ?
SF6 simulation
TransCom 2 experiment
NICAM
S. Denning et al., 1999
Comparison with TransCom continuous data
experiment models
NICAM
observation
fossil98
SF6
Inter-hemispheric transport of NICAM is still seemed to be stronger
SF6 observation data were downloaded from WDCGG site
Vertical transport: 222Rn simulation
Comparison with Jacob, et al., 1997
winter
summer
obs.
upper air
PBL
Green: other models, Blue: NICAM (V: not nudged, X: JRA, Y: NCEP)
Although there is an uncertainty of radon fluxes, the vertical transport simulated by NICAM is
seemed to be a little stronger than others in summer.
Comparison with continuous data at Hateruma
DJF
JJA
3
y  a0  a1 x   [a2i 1 sin( 2ix )  ai  2 cos( 2ix )] + R
SiB
i
CASA
blue:SiB, green:CASA, red:observation
Except in summer, high CO2 air from continental PBL was captured well.
Observation data were downloaded from WDCGG site
Comparison with aircraft data
Vertical profile @ Novosibirsk (West Siberia)
Boundary layer
was simulated
well
NICAM
Upper air by JAL airplane (Tokyo-Sydney)
observation
S ← latitude → N
convected high
CO2 air
OLR
Siberia data were provide by T. Machida (NIES)
JAL data were provided by H. Matsueda (MRI)
z
Summary and Perspective
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Introduction of NICAM
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Comparison with TransCom models
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Inter-hemispheric transport simulated by NICAM is stronger than
other models
The model results are in the range of other model results and in
good agreement with observations.
Comparison with observations
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NICAM is a new model developed as a global cloud resolving
model.
The grids of NICAM are very different.
Synoptic scale variations were captured well.
Small scale variation of atmospheric CO2 were reproduced.
Perspective
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Development of high-resolving inverse model
Thank you!
Acknowledgement
The datasets used for this study are provided from the cooperative research
project of the JRA-25 long-term reanalysis by Japan Meteorological Agency (J
MA) and Central Research Institute of Electric Power Industry (CRIEPI).
NCEP Reanalysis data were provided by the NOAA/OAR/ESRL PSD, Boulder,
Colorado, USA, from their Web site at http://www.cdc.noaa.gov/.
Aircrafts observation data at Siberia sites were offered from T. Machida (NIES)
and JAL observation data were offered from H. Matsueda (MRI).