Assessing the Lightning NOx Parameterization

in GEOS-Chem with HNO3 Columns from IASI

Matthew Cooper1

Randall Martin1,2, Catherine Wespes3,

Pierre-Francois Coheur3, Cathy Clerbaux3,4, Lee Murray5

1. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA3. Spectroscopie de l’Atmosphère, Chimie Quantique et Photophysique, Université Libre de Bruxelles, Brussels, Belgium4. Sorbonne Universités, UPMC Univ. Paris 06; Université Versailles St-Quentin; CNRS/INSU, LATMOS-IPSL, Paris, France5. NASA Goddard Institute for Space Studies and Lamont-Doherty Earth Observatory of Columbia University, NY, USA

𝑁𝑂𝑁𝑂2

𝑂3

𝐶𝑂

𝐻𝑁𝑂3

20-24 Tg

3-13 Tg

4-15 Tg

4-8 Tg

HNO3 Observations Can Be Used To Constrain NOx Emission Inventories

𝑂𝐻

GEOS-Chem HNO3 Biased Low Over SE AsiaIASI Annual Mean Tropospheric HNO3 Column

mole

c/cm

2

IASI – GEOS-Chem Percent Difference

mole

c/cm

2Pe

rcent

GEOS-Chem Annual Mean Tropospheric HNO3 Column

CO Observations Can Identify Transport Of Combustion Sources

Anthropogenic, Biomass burning sources emits NOx, CO

Long lifetime of CO allows for evaluation of transport

Lightning NOx source is independent CO

GEOS-Chem has 4 lightning regimes: Land – Ocean – Tropics – Midlatitudes

SE Asia lightning properties are different, which may lead to biases

Sim

ula

ted

IC/C

G F

lash

Rati

o

Regional Variations In Lightning Properties Not Captured By GEOS-Chem

Simulated IC/GC Flash Ratio

Flash

Footp

rint

[km

2]600

400

200

0

Lightning Properties Observed from Space [Beirle et al., 2014]

The GEOS-Chem Lightning NOX Parameterization

Prescribed NOx/flash(260 mol/flash)

Flash rates match satellite observations

Prescribed vertical profiles

Emissions added

to GEOS-Chem

4°x5° grid boxes

LNOx Plumes have Sub-Grid Spatial Scale.NOx Chemistry is Non-linear.

Early subgrid plume has high NOx concentration

Leads to rapid HNO3 production, lower OPE

This is not represented in the model

ActualPlume

PH

NO

3 (

mole

c cm

-3 s

-1) /

OPE (

mol/m

ol)

4°x5° GC grid box

NOx concentration (ppbv)

A Simple LNOx Plume Pre-processor

GC Grid BoxNOx

HNO3 + 15O3

Current Mechanism With Pre-Processing

• Adding 0.5 Tg N to Southeast Asia gives better agreement

GC Grid Box

NOx

-1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0

HNO3 Tropospheric Column (IASI – Standard GEOS-Chem)/IASI (IASI – GC w/ PreProcessor)/IASI

92% Bias

6% Bias

Conclusions

GEOS-Chem underestimates HNO3 in Southeast Asia

Lightning NOx is most likely contributor to bias

A preprocessor representing early stages of lightning plume improves the simulation

Bonus Slides

Inferring Tropospheric Contribution to Total Column Apply IASI averaging kernel to GC output = “total column”

Set GC troposphere to zero then apply kernel = “strat column” Infer tropospheric column = “total” – “strat”

Sensitivity

GC Total HNO3 Column Total Column Smoothed w/ IASI Kernel

GC Tropospheric HNO3 Column

Alt

itude (

hPa

)

IASI Vertical Sensitivity

Tropospheric Column Smoothed w/ IASI Kernel

Convective Effects

Scaled Mass Flux by 25% Scaled scavenging efficiency by 50%

Southeast Asia/ West Pacific is highly convective region HNO3 highly soluable – easily washed out Can have an impact, but its small

20% change vs 200% bias

GEOS-Chem lightning scaled by observed flash density

SE Asia lightning flashes are longer, more radiant than elsewhere in tropics

Intra-cloud lightning more common in SE Asia

[Beirle et al., Nat. Hazards Earth. System. Sci. Discuss, 2014]

Sim

ula

ted

IC/C

G F

lash

R

ati

o

Some Regionally Varying Lightning Properties that could Affect SE Asia

Lightning Properties Observed by OTD/LIS

Simulated IC/GC Flash Ratio

Vertical Distribution of NOx Emissions

NOx lifetime increases with altitude

Not much change in column near emissions region Change (~30%) is small compared to the bias vs IASI

(~200%)

Tropospheric HNO3 Column Ratio: Adjusted/Standard 1.

3

1.2

1.1

1

.9

.8

.7

Vertical Distribution

LNOx Plume Pre-processor VS

Prescribed Flash Yield• Adding 0.5 Tg N to Southeast Asia gives better

agreement

OzonesondeStandard3.5x Nox

Pre-Process

HNO3 Tropospheric Column(IASI – Standard GEOS-Chem)/IASI

(IASI –GEOS-Chem w/ Pre-Processor)/IASI