OBSERVATION OF ATMOSPHERIC COMPOSITION FROM SPACEOBSERVATION OF ATMOSPHERIC COMPOSITION FROM SPACE

Daniel J. Jacob, Harvard University

NASA NASA Earth & Sun Earth & Sun SpacecraftSpacecraft

STRATOSPHERIC OZONE HAS BEEN MEASURED STRATOSPHERIC OZONE HAS BEEN MEASURED FROM SPACE SINCE 1979FROM SPACE SINCE 1979

Method: UV solar backscatter

Scattering by Earth surface and atmosphere

Ozone layer

Ozoneabsorptionspectrum

ATMOSPHERIC COMPOSITION RESEARCH IS NOW MORE ATMOSPHERIC COMPOSITION RESEARCH IS NOW MORE DIRECTED TOWARD THE TROPOSPHEREDIRECTED TOWARD THE TROPOSPHERE

Tropopause

Stratopause

Stratosphere

Troposphere

Ozonelayer

Mesosphere

…but tropospheric composition measurements from space are difficult:optical interferences from water vapor, clouds, aerosols, surface, ozone layer

Air quality, climate change, ecosystem issues

WHY OBSERVE TROPOSPHERIC COMPOSITION FROM SPACE?WHY OBSERVE TROPOSPHERIC COMPOSITION FROM SPACE?

Monitoring and forecastingof air quality: ozone, aerosols

Long-range transport of pollution

Monitoring of sources:pollution and greenhousegases

• solar backscatter• thermal emission• solar occultation• lidar

FOUR OBSERVATIONMETHODS:

Global/continuous measurement capability important for range of issues:

Radiative forcing

SOLAR BACKSCATTER MEASUREMENTS (UV to near-IR)SOLAR BACKSCATTER MEASUREMENTS (UV to near-IR)

absorption

wavelength

Scattering by Earth surface and by atmosphere

Examples: TOMS, GOME, SCIAMACHY, MODIS, MISR, OMI, OCO

Pros:• sensitivity to lower troposphere• small field of view (nadir) Cons:

• Daytime only• Column only• Interference from stratosphere

concentration

Retrieved column in scattering atmospheredepends on vertical profile; need chemical transportand radiative transfer models

z

THERMAL EMISSION MEASUREMENTS (IR, THERMAL EMISSION MEASUREMENTS (IR, wave)wave)

EARTH SURFACE

I(To)

Absorbing gas

To

T1

I(T1)LIMB VIEW

NADIRVIEW

Examples: MLS, IMG, MOPITT, MIPAS, TES, HIRDLS, IASI

Pros:• versatility (many species)• small field of view (nadir)• vertical profiling

Cons:• low S/N in lower troposphere• water vapor interferences

OCCULTATION MEASUREMENTS (UV to near-IR)OCCULTATION MEASUREMENTS (UV to near-IR)

EARTH

“satellite sunrise”

Tangent point; retrieve vertical profile of concentrations

Examples: SAGE, POAM, GOMOS

Pros:• large signal/noise• vertical profiling Cons:

• sparse data, limited coverage• upper troposphere only• low horizontal resolution

LIDAR MEASUREMENTS (UV to near-IR)LIDAR MEASUREMENTS (UV to near-IR)

EARTH SURFACE

backscatter by atmosphere

Laser pulse

Examples: LITE, GLAS, CALIPSO

Intensity of return vs. time lag measures vertical profile

Pros: • High vertical resolution

Cons:• Aerosols only (so far)• Limited coverage

ALL ATMOSPHERIC COMPOSITION DATA SO FAR HAVE BEEN ALL ATMOSPHERIC COMPOSITION DATA SO FAR HAVE BEEN FROM LOW-ELEVATION, SUN-SYNCHRONOUS POLAR ORBITERSFROM LOW-ELEVATION, SUN-SYNCHRONOUS POLAR ORBITERS

• Altitude ~ 1,000 km

• Observation at same time of day everywhere

• Period ~ 90 min.

• Coverage is global but sparse

TROPOSPHERIC COMPOSITION FROM SPACE:TROPOSPHERIC COMPOSITION FROM SPACE:platforms, instruments, speciesplatforms, instruments, species

Sensor TOMS GOME MOPITT MISR MODIS AIRS SCIA-MACHY

TES MLS OMI OCO

Platform (launch)

multi

(1979-)

ERS-2 (1995)

Terra Aqua

(1999) ( 2002)

Envisat (2002)

Aura

(2004) 2008

ozone X (tro-pics)

X X X X

CO X X X X

CO2 X

CH4 X

NO2 X X X

HNO3 X

HCHO X X

BrO X X

aerosol X X

NASA AURA SATELLITE (launched July 2004)NASA AURA SATELLITE (launched July 2004)

AuraAuraMLS

TES nadirTES nadirOMIOMI

HIRDLS Direction of motion

TES limbTES limb

Polar orbit; four passive instruments observing same air mass within 14 minutes

•OMI: UV/Vis solar backscatter• NO2, HCHO. ozone, BrO columns

• TES: high spectral resolution thermal IR emission• nadir ozone, CO• limb ozone, CO, HNO3

•MLS: microwave emission• limb ozone, CO (upper troposphere)

• HIRDLS: high vertical resolution thermal IR emission• ozone in upper troposphere/lower stratosphere

Tropospheric measurement capabilities:

OBSERVING TROPOSPHERIC OZONE AND ITS SOURCES FROM SPACE

Nitrogen oxide radicals; NOx = NO + NO2

Sources: combustion, soils, lightningMethaneSources: wetlands, livestock, natural gasNonmethane VOCs (volatile organic compounds)Sources: vegetation, combustionCO (carbon monoxide)Sources: combustion, VOC oxidation

Troposphericozone

precursors

CONSTRAINING NOCONSTRAINING NOxx AND REACTIVE VOC EMISSIONS AND REACTIVE VOC EMISSIONS

USING SOLAR BACKSCATTER MEASUREMENTSUSING SOLAR BACKSCATTER MEASUREMENTSOF TROPOSPHERIC NOOF TROPOSPHERIC NO22 AND FORMALDEHYDE (HCHO) AND FORMALDEHYDE (HCHO)

Emission

NOh (420 nm)

O3, RO2

NO2

HNO3

1 day

NITROGEN OXIDES (NOx) VOLATILE ORGANIC COMPOUNDS (VOC)

Emission

VOC

OHHCHOh (340 nm)

hoursCO

hours

BOUNDARYLAYER

~ 2 km

Tropospheric NO2 column ~ ENOx

Tropospheric HCHO column ~ EVOC

Deposition

GOME: 320x40 km2

SCIAMACHY: 60x30 km2 OMI: 24x13 km2

K. Folkert Boersma (Harvard)

TROPOSPHERIC NOTROPOSPHERIC NO22 FROM OMI: CONSTRAINT ON NO FROM OMI: CONSTRAINT ON NOxx SOURCES SOURCES

October 2004

K. Folkert Boersma (Harvard)

TROPOSPHERIC NOTROPOSPHERIC NO22 FROM OMI: ZOOM ON U.S. AND MEXICO FROM OMI: ZOOM ON U.S. AND MEXICO

MILAGRO campaign, March 2006

1996-2005 TREND IN NO1996-2005 TREND IN NOxx EMISSIONS SEEN FROM SPACE EMISSIONS SEEN FROM SPACE Van der A et al., in prep.

FORMALDEHYDE COLUMNS MEASURED BY GOME FORMALDEHYDE COLUMNS MEASURED BY GOME (JULY 1996) (JULY 1996)

High HCHO regions reflect VOC emissions from fires, biosphere, human activity

-0.5

0

0.5

1

1.5

2

2.5x1016

moleculescm-2

SouthAtlanticAnomaly(disregard)

detectionlimit

FORMALDEHYDE COLUMNS FROM OMI OVER U.S. (July 2005):FORMALDEHYDE COLUMNS FROM OMI OVER U.S. (July 2005): biogenic isoprene is the principal reactive VOC biogenic isoprene is the principal reactive VOC

OMIGEOS-Chem chemical transport model

with best prior estimates of VOC emissions

Dylan B. Millet (Harvard) and Thomas Kurosu (Harvard-SAO)

SEASONALVARIATION OF GOME FORMALDEHYDE COLUMNS SEASONALVARIATION OF GOME FORMALDEHYDE COLUMNS reflects seasonal variation of biogenic isoprene emissionsreflects seasonal variation of biogenic isoprene emissions

SEP

AUG

JUL

OCT

MAR

JUN

MAY

APR

GOME GEOS-Chem (GEIA) GOME GEOS-Chem (GEIA)

Abbot et al. [2003]

GOME JJA 1997 tropospheric columns (Dobson Units)

TROPOSPHERIC OZONE OBSERVED FROM SPACETROPOSPHERIC OZONE OBSERVED FROM SPACE

Is there a summer maximum over the Middle East?

GEOS-Chem model maximum [Li et al., GRL 2001]:

Is it real?

IR emission measurement from TES UV backscatter measurement from GOME

Liu et al., 2006

TES ozone and CO observations in July 2005 at 618 hPaTES ozone and CO observations in July 2005 at 618 hPa

TES observations of ozone-CO correlations can test CTM simulations of ozone continental outflow

North America

Asia

Zhang et al., 2006

USING ADJOINTS OF CHEMICAL TRANSPORT MODELS TO USING ADJOINTS OF CHEMICAL TRANSPORT MODELS TO INVERT FOR EMISSIONS WITH HIGH RESOLUTIONINVERT FOR EMISSIONS WITH HIGH RESOLUTION

MOPITT daily CO columns(Mar-Apr 2001) Correction to model

sources of CO

A priori emissions fromStreets et al. [2003] andHeald et al. [2003]

Monika Kopacz, Harvard

Inverse ofatmospheric

model

(sensitivity)

OBSERVING COOBSERVING CO22 FROM SPACE: FROM SPACE:

Orbiting Carbon Observatory (OCO) to be launched in 2008Orbiting Carbon Observatory (OCO) to be launched in 2008

Polar-orbiting solar backscatter instrument, measures CO2 absorption at 1.61 and 2.06 m, O2 absorption (surface pressure) at 0.76 m: global mapping of CO2 column mixing ratio with 0.3% precision

Averaging kernel

Pre

ss

ure

(h

Pa

)

OCO will provide powerful constraintson regional carbon fluxes

UV-IR sensors would provide continuous high-resolution mapping (~1 km)

on continental scale: boon for air quality monitoring and forecasting

LOOKING TOWARD THE FUTURE: LOOKING TOWARD THE FUTURE: GEOSTATIONARY ORBITGEOSTATIONARY ORBIT

LAGRANGE POINTS MISSION CONCEPTSLAGRANGE POINTS MISSION CONCEPTS

L1: view full disk of sunlit Earth• nadir obs as in geostationary• continuous obs from sunrise to sunst

L2: nighttime Earthcontinuous solaroccultation measurements

PROPOSED L-1 MISSION TO NASAPROPOSED L-1 MISSION TO NASA(Janus)(Janus)

L-1 point : 1.5 million km from Earth along Earth- Sun line

NH and SH summer views from L-1:global continuous daytime coverage

• Continuous global observation of Earth sunlit disk with 5 km nadir resolution

• UV-IR spectrometers for observation of ozone, NO2, HCHO, CO, aerosols, CO2, methane

• Global continuous view from L-1 critical for observation of hemispheric pollution, tropospheric background, greenhouse gases

• Bridge with interests of climate, upper atmosphere, space weather, solar physics communities

Satellites

OBSERVING SYSTEM FOR ATMOSPHERIC COMPOSITIONOBSERVING SYSTEM FOR ATMOSPHERIC COMPOSITIONMUST INTEGRATE SATELLITES, IN SITU MEASUREMENTS, AND MODELSMUST INTEGRATE SATELLITES, IN SITU MEASUREMENTS, AND MODELS

Surface monitors

Chemical transport

models

Aircraft, lidar

NEW KNOWLEDGE

Air quality monitoring& forecasting

Source quantification,policing of environ-mental agreements

Long-range transport

Climate forcing

Biogeochemical cycling

Weather forecasting