Yingying Yan 燕莹莹 , Jintai Lin 林金泰 , Xiong Liu, Jinxuan Chen

School of Physics, Peking University

Tropospheric Ozone in Two-way Coupled Model of GEOS-Chem

• 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

rAB < 0: Model has an overestimation

rAB > 0: Model has an underestimation

2

BAABrBABABA ''

Limited by ResolutionModels Misrepresent Small-scale Processes

Developments by regional modelsGround-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

4

• 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

Global-multi-regional Two-way Coupled Modeling

5

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

Global ↔ Regional Model Interaction Scheme

6

Files in the new PKUCPL subdirectory:1. Twoway.compile.sh: compile 2-way modeling2. PKUCPL.F90: modulate the normal DO-Loop, to coordinate all models3. PKUCPL.sh: provide utility to run models in the right directories4. run: ./run 2cne (couple global model (2x2.5) with three nested models)

Steps: 1. Set up the run directories2. Compile for two-way coupled model ./Twoway.compile.sh3. 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

Coupled simulation setup steps

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

Tropospheric Column OzoneM

AM

DJF

SO

NJJ

A

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%)

10

• 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.

Yan Y.-Y. et al., 2014, ACP

Improvements in CO Simulation

11

Yan Y.-Y. et al., 2014, ACP; 2015, in prep

* 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

Global Model Two-way Model ‘Observation’

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 ( + 10.8% &)

NMVOC (TgC) 10.1 10.2

Improvements in tropospheric Simulation