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 NICAM was first developed by Satoh (CCSR/FRCGC)　 and

H. Tomita (FRCGC).(H. Tomita and M. Satoh, 2004, M. Satoh et al., 2007)

Developed as a global cloud resolving model (GCRM).The max resolution… dx~3.5km

NICAM is also used as a low-resolution Atmospheric Circulation Model (AGCM) and as a regional model (Stretch-NICAM).I used NICAM as a AGCM and modified it an on-line tracer transport model.

I added new tracers and developed nudging moduleresolution…dx~240km

Realistic experiment by NICAM

OLR (by H. Miura) http://www.ccsr.u-tokyo.ac.jp/~satoh/nicam/index.html

dx~3.5km

A 3.5km-mesh global simulation was performed using the Earth Simulator. (H. Miura et al., 2007)

Grids of NICAM

sT

sT

zz

zzzz

)(

*

recursively divided

Horizontal grid:

Vertical grid:

Terrain-following coordinate: *z

level sea aboveheight :

location) horizontalon (dependsheight surface :

domain model of top:

z

z

z

s

T

It looks like σ coordinate, but doesn’t depends on pressures and is not time-variable.

Regional model version:

stretched gridicosahedral grid

Advantages of NICAM for tracer transport simulations 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 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

The North-South gradient simulated by NICAM is smaller than other models.

Surface 500hPa

tracer : fossil fuel 1990

Evaluation of meridional transport comparison with TransCom 3 models ②

stronger inter-hemispheric transport

TransCom 3 models

NICAM

tracer : fossil fuel 1990

CTL

Nudged

sub-grid transport by cumulus convection was reduced by half

½ cumulus effect

dynamical field simulated by NICAM is not problem

cumulus convection hardly affect!

Large scale advection is the cause of inter-hemispheric transportDue to the advection scheme of NICAM ?

SF6 simulationTransCom 2 experiment

S. Denning et al., 1999NICAM

Comparison with TransCom continuous data experiment models

fossil98 SF6

SF6 observation data were downloaded from WDCGG site

Inter-hemispheric transport of NICAM is still seemed to be stronger

NICAM

observation

Vertical transport: 222Rn simulationComparison with Jacob, et al., 1997

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.

summer winter

PBL

upper airobs.

Comparison with continuous data at Hateruma

)]2cos( )2sin([ 2

3

1210 ixaixaxaay ii

i + R

Observation data were downloaded from WDCGG site

DJF JJA

Except in summer, high CO2 air from continental PBL was captured well.

SiB CASA

blue:SiB, green:CASA, red:observation

Comparison with aircraft dataVertical profile @ Novosibirsk (West Siberia)

Upper air by JAL airplane (Tokyo-Sydney)Boundary layer was simulated well

z

S ← latitude → N

convected high CO2 air

OLR

Siberia data were provide by T. Machida (NIES)JAL data were provided by H. Matsueda (MRI)

NICAM observation

Summary and Perspective Introduction of NICAM

NICAM is a new model developed as a global cloud resolving model.

The grids of NICAM are very different. Comparison with TransCom models

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 Synoptic scale variations were captured well. Small scale variation of atmospheric CO2 were reproduced.

Perspective Development of high-resolving inverse model

Thank you!

AcknowledgementThe 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).