Dalhousie UniversityDalhousie UniversityDepartment of Physics and Atmospheric ScienceDepartment of Physics and Atmospheric Science

• Materials Science

• Biophysics

• Condensed Matter Physics

• Atmospheric Science

Research in Theoretical, Experimental, and Applied Physics

http://www.physics.dal.ca/files/Physics_and_Atmospheric_Science_Faculty.ppt

Ozone and Aerosols in the Lower AtmosphereOzone and Aerosols in the Lower Atmosphere

Randall MartinAaron Van Donkelaar Arlene Fiore

Kelly Chance Chris Sioris

GLOBAL RADIATIVE FORCING OF CLIMATE, GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present1750-present

IPCC [2001]

ORIGIN OF ATMOSPHERIC AEROSOLSORIGIN OF ATMOSPHERIC AEROSOLS

Soil dustSea salt

Aerosol: dispersed condensed matter suspended in a gasSize range: 0.001 m (molecular cluster) to 100 m (small raindrop)

Environmental importance: health (respiration), visibility, radiative balance,cloud formation, heterogeneous reactions, delivery of nutrients…

Toronto (1997-99)Egbert (1994-99)

Abbotsford (1994-95)

Quaker City OH (1999)

Arendstville PA (1999)

Atlanta (1999)Yorkville (1999)Mexico City - Pedregal (1997)

Los Angeles (1995-96)

Fresno (1988-89)

Kern Wildlife Refuge (1988-89)

Sulfate

Nitrate

Ammonium

Black carbon

Organic carbon

Soil

Other

12.3 ug m-38.9 ug m-3

7.8 ug m-3

12.4 ug m-3

10.4 ug m-3

19.2 ug m-314.7 ug m-3

55.4 ug m-3

30.3 ug m-3

23.3 ug m-3

39.2 ug m-3

Washington DC (1996-99)

14.5 ug m-3

Colorado Plateau (1996-99)3.0 ug m-3

Mexico City - Netzahualcoyotl (1997)

24.6 ug m-3

Esther (1995-99)

St. Andrews (1994-97)5.3 ug m-3

4.6 ug m-3

COMPOSITION OF PM2.5 COMPOSITION OF PM2.5 (NARSTO PM ASSESSMENT)(NARSTO PM ASSESSMENT)

Scattering of Radiation

Size Parameter: xr

Mie Theory

Extinction = Scattering + Absorption

Extinction Efficiency (Qext) = ratio of the extinction cross section to the geometric cross-section (πr2)

MODerate-resolution Imaging Spectroradiometer MODerate-resolution Imaging Spectroradiometer (MODIS)(MODIS)

Seven MODIS bands are available for aerosol properties

0.47, 0.55, 0.65, 0.86, 1.24, 1.64, and 2.13 µm

OCEAN

reflectance contrast between cloud-free atmosphere and dark ocean

aerosol optical thickness for all 7 bands

LAND

reflectance of dark vegetation and semi-arid regions deduced using 2.13 µm where

aerosols are nearly transparent

reflectance contrast between atmosphere and dense dark vegetation surface

aerosol optical thickness (0.47 and 0.66 µm)

0 0

2 dzdrrnrQext

Optical Thickness

I=Ioe-

Apollo 17 1972 What do we

actually see?

Mar 3, 2003

Aerosols Visible over Dark Surface

Example Cloud and Aerosol Optical ThicknessExample Cloud and Aerosol Optical Thickness

Aerosol Optical Thickness (550 nm)

Cloud Optical Thickness

TROPOSPHERIC OZONE IS A KEY SPECIES IN CLIMATE AND TROPOSPHERIC OZONE IS A KEY SPECIES IN CLIMATE AND AIR QUALITYAIR QUALITY

Tropopause

Stratopause

•Major greenhouse gas

•Primary constituent of smog

•Largely controls atmospheric oxidation

Stratosphere

Troposphere

Ozonelayer

Mesosphere

THE ATMOSPHERE IS AN OXIDIZING MEDIUM THE ATMOSPHERE IS AN OXIDIZING MEDIUM

EARTHSURFACE

Emission

Reduced gasOxidized gas/aerosol

Oxidation

Uptake

Reduction

CO, VOCs, NOx

HO2OH

NONO2

H2O2

O3

hv, H2O

hvHNO3

OH

VOCs + OH HCHO

HCHO + h 2HO2 + CO

HCHO + OH HO2 + CO + H2O

CO, VOCs

Simplified Tropospheric Ozone (O3) Chemistry

Role of Formaldehyde (HCHO)

NOx

HOx

THE NITROGEN CYCLE: MAJOR PROCESSESTHE NITROGEN CYCLE: MAJOR PROCESSES

ATMOSPHEREN2 NO

HNO3

NH3/NH4+ NO3

-

orgN

BIOSPHERE

LITHOSPHERE

combustionlightning

oxidation

deposition

assimilation

decay

nitrification

denitri-ficationbiofixation

burial weathering

NONOxx EMISSIONS (Tg N yr EMISSIONS (Tg N yr-1-1) TO TROPOSPHERE) TO TROPOSPHERE

FOSSIL FUEL 20

AIRCRAFT 0.5

BIOFUEL 2

BIOMASSBURNING 5

SOILS 5

LIGHTNING 6

STRATOSPHERE 0.2

EULERIAN EULERIAN RESEARCH MODELS SOLVE MASS BALANCE RESEARCH MODELS SOLVE MASS BALANCE

(alias CONTINUITY) EQUATION IN 3-D ASSEMBLAGE OF (alias CONTINUITY) EQUATION IN 3-D ASSEMBLAGE OF GRIDBOXES GRIDBOXES

Solve continuity equation for individual gridboxes

• Models can presently afford ~ 106 gridboxes

• In global models, this implies a horizontal resolution of 100-500 km in horizontal and ~ 1 km in vertical

DELPz

u

y

u

x

un

t

n zyx

BOTTOM-UP EMISSION INVENTORIES ARE BOTTOM-UP EMISSION INVENTORIES ARE NOTORIOUSLY DIFFICULT TO DETERMINENOTORIOUSLY DIFFICULT TO DETERMINE

• Fuel use estimates• Measurements of emission ratios• Process studies• Estimate biological density• Temperature, water, … dependence

of biological activity• Extreme events

1E+08

1E+10

1E+12

1E+14

1E+16

200 300 400 500 600 700 800Wavelength [nm]

Inte

nsity [a

rbitra

ry u

nits]

O3 UV

O3 vis

HCHO

OClO

O4

O2

H2O

SO2 NO2

BrO

Satellite group: http://giger.iup.uni-heidelberg.de/

Absorbing properties of molecules

Atmospheric trace gas absorptions detected in satellite spectra:

Retrieval of Trace Gas ColumnRetrieval of Trace Gas Column

EARTH SURFACE

Scattering by Earth surface and by atmosphere

Backscatteredintensity IB

Solar Io

RingeIAI s

B )()()( 0

A

Nonlinear least-squares fitting

Total NOTotal NO22 Slant Columns Observed from the SCIAMACHY Slant Columns Observed from the SCIAMACHY

Satellite InstrumentSatellite Instrument

May-August 2004

Perform a Radiative Transfer Calculation to Account for Viewing Perform a Radiative Transfer Calculation to Account for Viewing Geometry and ScatteringGeometry and Scattering

Cloud Screening: Remove Scenes with ICloud Screening: Remove Scenes with IB,c B,c > I> IB,oB,o

RcRo

IB,o IB,c

Pc

Rs

•LIDORT Radiative Transfer Model [Spurr et al., 2002]

•FRESCO Clouds Fields [Koelemeijer et al., 2002]

•GOME Surface Reflectivity [Koelemeijer et al., 2003]

d

Io

Tropospheric NOTropospheric NO22 Columns Observed from the SCIAMACHY Columns Observed from the SCIAMACHY

Satellite InstrumentSatellite Instrument

May-August 2004

detectionlimit

Major Urban Centers Are Concentrated NOx SourcesMajor Urban Centers Are Concentrated NOx Sources

May-August 2004

detectionlimit

Sillman and He, 2002

(ppbv)

NOx-Saturated

NOx-Limited

Shown that the HCHO/NO2 Ratio Is as IndicatorThat Can be Observed from Space

Ozone Control Strategies Require Independent Ozone Control Strategies Require Independent Information on Effectiveness of Reducing NOx or VOCsInformation on Effectiveness of Reducing NOx or VOCs

GOME Observations Show NOGOME Observations Show NOxx-Sensitive Conditions -Sensitive Conditions

Over Most Polluted Regions During AugustOver Most Polluted Regions During AugustMajor Industrial Areas are Clear ExceptionsMajor Industrial Areas are Clear Exceptions

August

White areas indicate clouds or data below the GOME detection limit

Biomass Burning Emissions are Clearly NOBiomass Burning Emissions are Clearly NOxx-Sensitive, -Sensitive,

In Contrast with NOIn Contrast with NOxx-Saturated Conditions Over the -Saturated Conditions Over the

Industrial Highveld Industrial Highveld

August

Also observe plume evolution

NO

x L

im

NO

x L

im

Seasonal Seasonal Evolution from Evolution from

NOx-Sensitive to NOx-Sensitive to NOx-Saturated NOx-Saturated

Conditions in FallConditions in Fall