Tropospheric Ozone in Two-way
Coupled Model of GEOS-Chem
Yingying Yan 燕莹莹, Jintai Lin 林金泰, Xiong Liu, Jinxuan Chen
School of Physics, Peking University
Limited by Resolution
Models Misrepresent Small-scale Processes
•
•
•
•
•
Un-even terrain
Small-scale meteorology
Variability in land use, vegetation, etc.
Small-scale horizontal & vertical transport
Small-scale variability in chemistry & emissions
model reality
A  B  A  B   A'  B '  rAB   A   B
 rAB < 0:
 rAB > 0:
Model has an overestimation
Model has an underestimation
2
Developments by regional models
Ground-level NMVOCs/NOx ratio and ozone diff.
 Emissions
•
•
Small-scale variability smoothed
Resolution-dependent natural emission
(6.5% higher in biogenic NMVOCs)
 Ozone production regime: 20
 Negative diff. : East China
East America
Europe
 Positive diff. : Tibet Plateau
Rocky Mountains
 Topography smoothed
Global-multi-regional Two-way Coupled Modeling
•
•
•
•
High-res regional nested simulations ‘correct’ global model
Global and multiple regional models interact simultaneously
High computation efficiency and low model complexity
Differences can be transported to outside the nested domains and
accumulate during the lifetime of chemical species
Global model : ~ 200km res.
Regional models: ~ 50 km res.
Yan Y.-Y. et al., 2014, ACP
4
Global ↔ Regional Model Interaction Scheme
Simulation flowchart
• Global v.s. regional models:
– Different horizontal resolutions
– Consistent data inputs
•
•
•
•
Multi models run independently
Models ‘talk’ via simple I/O files
Low CPU and I/O burdens
Fast calculation
Yan Y.-Y. et al., 2014, ACP
5
Coupled simulation setup steps
Files in the new PKUCPL subdirectory:
1. Twoway.compile.sh: compile 2-way modeling
2. PKUCPL.F90: modulate the normal DO-Loop, to coordinate all models
3. PKUCPL.sh: provide utility to run models in the right directories
4. run: ./run 2cne (couple global model (2x2.5) with three nested models)
Steps:
1. Set up the run directories
2. Compile for two-way coupled model
./Twoway.compile.sh
3. submit the batch job script 'run_twoway' for two-way simulation
qsub run_twoway
(See http://wiki.seas.harvard.edu/geos-chem/index.php/Two-way_nesting_in_GEOS-Chem)
Development in the future:
Easy to include the newly built and higher resolution nested models
6
Easy O(∩_∩)O Flexible \(^o^)/ Cool to run all models coupled in parallel
Better simulation of ground-level ozone
 Mean R increases from 0.51 to 0.65
 Mean bias decreases by 4.8 ppb
Yan Y.-Y. et al., 2015, in prep
Tropospheric ozone profile
Obs Two-way Global
MAM
Tropospheric Column Ozone
DJF
SON
JJA
 OMI_MEAN=(OMI/MLS + OMI/LIU)/2
 2-way minus global: 3.2 DU (8.9%)
 2-way – OMI_MEAN:
MAM: 2.2 DU (6.5%)
JJA: -0.7 DU (-1.7%)
SON: 1.6 DU (5.6%)
DJF: -0.8 DU (-2.1%)
Improvements in CO Simulation
• 2-way ~ (Global + CO emis)
HIPPO-1: + 15%
HIPPO-2: + 25%
HIPPO-3: + 15%
HIPPO-4: + 25%
HIPPO-5: + 35%
Mean : + 25%
It is an important model
dependence on resolution
that is largely unaccounted
for CO emission constraints.
10
Yan Y.-Y. et al., 2014, ACP
Improvements in tropospheric Simulation
‘Observation’
Global Model
Two-way Model
OH (105 cm-3)
11.8
11.2
( – 5% * )
10.4 – 10.9
MCF lifetime (yr)
5.58
5.87
( + 5.2% )
6.0 – 6.3
CH4 lifetime (yr)
9.63
10.12 ( + 5.1% )
10.2 – 11.2
O3 (DU)
34.5
31.5
( – 8.7% )
31.1 ± 3
(OMI/MLS)
O3 (Tg)
384
348
( – 9.4% # )
NOx (TgN)
0.169
0.176 ( + 4.1% )
CO (Tg)
359
398
NMVOC (TgC)
10.1
10.2
( + 10.8% &)
* Greater than its interannual variability (2.3%)
# Greater than the change from 2000 to 2100 under RCP6.0
& Equivalent to a 25% increase in global CO emissions
11
Yan Y.-Y. et al., 2014, ACP; 2015, in prep