Model Simulation of tropospheric BrO

Xin Yang, J. Pyle and R. Cox

Center for Atmospheric ScienceUniversity of Cambridge

7-9 Oct. 2007. Frascati, Italy

Basic model information• Model: a 3D global chemical transport model, p-TOMCAT, with detailed

bromine chemistry [Yang et al., JGR, 2005].

• Br sources: 6 bromocarbons and sea salt from both open ocean and polar sea ice surface due to wind-driven production. A new size-dependent Br depletion factor for sea salt aerosols

• Br-Chemistry: adding 3 heterogeneous reactivations on aerosols, such as HBr+HOBr—Br2+H2O

• Forcing field: ECWMF reanalysis data (every 6hrs)

• Resolutions: T42 (2.8x2.8 degrees) x 31 vertical layers

• Simulation period: 1998

• Output frequency: 2hrs (to match GOME SZA for BrO)

HBr, HOBr, Br2

wet or dry deposition

Bromine chemical scheme in p-TOMCAT model

BrO

Br

BrONO2

HOBr

Br2

O3

NO, OH, RO2, BrO

NO2

HO2,RO2

HO2, RO2, HCHO, RCHO

hv

hv, OH

hv

hv

BrNO2

NO2 hv

hv

HBrOH

BrO

Br

hv

Cloud particles

HNO3

Sea salt aerosols

N2O5

Ocean, land, polar sea ice

CH3Br, CHBr3,CH2Br2, CH2BrCl,CHBr2Cl, CHBrCl2

OH hv

Ocean sea salt

~0.62 TgBr/yr

~1-2 TgBr/yr

Sea ice sea salt

Comparison with GOME in March

The upper figure is the simulated monthly mean (March) daytime (9am-3pm) tropospheric column BrO(×1013 molecules/cm2 ). The bottom figure is GOME BrO – trop+strat

Basically, the model captured the main feature of the GOME BrO in arctic with large level along Arctic coasts and over northern American (Good).

An exception is over Greenland sea where model see a big BrO but GOME did not (Good or bad?)

Satellite is less sensitive over open water?

In SH, its autumn tropospheric BrO is about 2 × 1013 molecules/cm2, about 2 times of NH autumn level (Good)

In the tropics, the lowest tropospheric BrO is 0.5 × 1013 molecules/cm2

Comparison with GOME in Sep.

• Basically, the model captured the main structure of the ring-like high BrO around Antarctic during SH spring. Good

• The simulated BrO in SH spring is higher than that in the NH spring. (Bad ?)

• If model problem: • 1) overestimated Br depletion

factor for seasalts • 2) not including humidity effect on

sea salt production

• If true: underestimated by satellite due to less ice cover in Southern Ocean

• • In NH, its autumn tropospheric

BrO is about 1 × 1013 molecules/cm2, which is only half of SH autumn level (Good).

Over Barrow

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Julian Day

Ve

rtic

al c

ou

lum

n B

rO (

*1E

13

mo

lec

/cm

^2

)

GOM E BrO over Barrow

SNOW run BrO

SEA ICE run BrO

OCEAN run brO

no-HET run BrO40

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0 200

J ulian day

y = 0.436x - 0.2225R2 = 0.2078

02468

10121416

0 5 10 15GOME BrO

SN

OW

run

BrO

In the NHOver Alert (82N, 62W)

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lum

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rO

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Model

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Julian day

SZ

A

GOME

Model

y = 0.8548x - 1.9117

R2 = 0.3298

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GOME

Mo

del

Over NyAlesund (79N, 12E)

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umn

BrO

GOME

Model40

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Julian day

SZ

A

GOME

Model

y = 1.1359x - 2.8656

R2 = 0.3558

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GOME

Mo

del

Over Summit (72N,38W)

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BrO

GOME

Model

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Julian day

SZ

A

GOME

Model

y = 0.3233x - 0.6274

R2 = 0.1812

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GOME

Mo

de

l

Over Harestua (60N, 11E)

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BrO

GOME BrO

Model BrO

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SZ

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GOME

Model

y = 0.5045x - 1.0852

R2 = 0.1709

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0 2 4 6 8

GOME

Mo

del

Over Harestua (60N, 11E)

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rO

GOME BrO

Model BrO

Comparison between ground-based UV-vis and modeled tropospheric and stratospheric BrO columns.

By Hendrick et al., ACP-2007-0224.

1998

In the SH

Over Neumayer (70S, 8W)

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BrO

GOME

Model40

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Julian day

SZ

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GOME

Model

y = 0.4275x + 0.8503

R2 = 0.0393

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GOME

Mo

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Over Arrival Height (78S, 170E)

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BrO

GOME

Model 40

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Julian day

SZ

A

Series1

Series2

y = -0.7881x + 7.8051

R2 = 0.1024

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GOME

Mo

del

Over Alert (82N, 62W)

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Julian day

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rO

GOME

Model

Over NyAlesund (79N, 12E)

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BrO

GOME

Model

Over Summit (72N,38W)

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rO

GOME

Model

Over Harestua (60N, 11E)

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Julian day

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lum

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rO

GOME BrO

Model BrO

Over Neumayer (70S, 8W)

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Julian day

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BrO

GOME

Model

Over Arrival Height (78S, 170E)

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Satellite can not see BrO explosions happened in early spring in the SH (?!)

This is consistent with ship measurement by Wagner et al., ACP, 2007

Zonal mean BrO (pptv)

O3 loss (%)

Possible further collaboration

We hope to work together with scientist in this fields to validate our model through more comparisons with derived-BrO data from both satellite and ground based measurements. These comparisons can be in short time scale, such as daily variation, or in long time scale, such as seasonal or year-to-year variation, even in long term trend.

We hope TEMIS to supply more satellite column BrO data on global scale for further comparison, especially over the sites where high BrO events frequently happen, such as coastal regions of Arctic, Hudson bay, in SH over Weddle Sea and Rose Sea.

We also hope observers to pay some attentions on the ‘potential high BrO plumes’ over regions where are open water in local spring. For example, over Greenland Sea and off the main ice sheet in the Southern Ocean.

Thanks

Invitation by TEMIS/SEA

EU project THALOZ

NCAS/NERC, UK

Ozone loss

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60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90

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n/w

ind

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960

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1020

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Pre

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(h

pa

)

O3 (SNOW run, ppbv)O3 (SEA ICE run, ppbv)O3 (OCEAN run. ppbv)O3 (no-HET run, ppbv)BrO (SNOW run, pptv)Brx (SNOW run, pptv)Model 10m wind (m/s) Observed daily mean wind (m/s)Observed max. wind (m/s)Model surface pressure (hpa)

Vertical diffusion and emission effects on O3 loss

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82 83 84 85 86 87 88 89 90

Julian day

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sp

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tio

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pp

tv)

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O3

co

nc

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tra

tio

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pp

bv

)

BrOx (no diff. and no emission)

BrOx (no diff. but w ith 1/10 emission)

Brx (no diff. but w ith 1/10 emission)

O3 (SNOW run)

O3 (no diff. and no emission)

O3 (no diff. but with 1/10 emission)