OBSERVATION OF ATMOSPHERIC COMPOSITION FROM SPACE

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OBSERVATION OF ATMOSPHERIC COMPOSITION FROM SPACE
Daniel J. Jacob, Harvard University
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NASA Earth Sun Spacecraft
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STRATOSPHERIC OZONE HAS BEEN MEASURED FROM SPACE
SINCE 1979
Method UV solar backscatter
l2
l1
Ozone layer
Scattering by Earth surface and atmosphere
Ozone absorption spectrum
l1
l2
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ATMOSPHERIC COMPOSITION RESEARCH IS NOW MORE
DIRECTED TOWARD THE TROPOSPHERE
Air quality, climate change, ecosystem issues
but tropospheric composition measurements from
space are difficult optical interferences from
water vapor, clouds, aerosols, surface, ozone
layer
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WHY OBSERVE TROPOSPHERIC COMPOSITION FROM SPACE?
Global/continuous measurement capability
important for range of issues
Monitoring and forecasting of air quality ozone,
aerosols
Long-range transport of pollution
Monitoring of sources pollution and
greenhouse gases
Radiative forcing

• solar backscatter
• thermal emission
• solar occultation
• lidar

FOUR OBSERVATION METHODS
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SOLAR BACKSCATTER MEASUREMENTS (UV to near-IR)
Examples TOMS, GOME, SCIAMACHY, MODIS, MISR,
OMI, OCO
absorption
l1
l2
z
l1
l2
wavelength
Retrieved column in scattering atmosphere depends
on vertical profile need chemical transport and
radiative transfer models
Scattering by Earth surface and by atmosphere
concentration

• Daytime only
• Column only
• Interference from stratosphere

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

Pros
Cons
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THERMAL EMISSION MEASUREMENTS (IR, mwave)
Examples MLS, IMG, MOPITT, MIPAS, TES, HIRDLS,
IASI
NADIR VIEW
LIMB VIEW
elIl(T1)
T1
Absorbing gas

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

Pros
Il(To)
To
EARTH SURFACE

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

Cons
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OCCULTATION MEASUREMENTS (UV to near-IR)
Examples SAGE, POAM, GOMOS
satellite sunrise
Tangent point retrieve vertical profile of
concentrations
EARTH

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

• large signal/noise
• vertical profiling

Pros
Cons
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LIDAR MEASUREMENTS (UV to near-IR)
Examples LITE, GLAS, CALIPSO
Pros

• High vertical resolution

Laser pulse

• Aerosols only (so far)
• Limited coverage

Cons
Intensity of return vs. time lag measures
vertical profile
backscatter by atmosphere
EARTH SURFACE
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ALL ATMOSPHERIC COMPOSITION DATA SO FAR HAVE BEEN
FROM 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

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TROPOSPHERIC COMPOSITION FROM SPACEplatforms,
instruments, species
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NASA AURA SATELLITE (launched July 2004)
Polar orbit four passive instruments observing
same air mass within 14 minutes
Tropospheric measurement capabilities

• 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

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OBSERVING TROPOSPHERIC OZONE AND ITS SOURCES FROM
SPACE
Nitrogen oxide radicals NOx NO NO2 Sources
combustion, soils, lightning Methane Sources
wetlands, livestock, natural gas Nonmethane VOCs
(volatile organic compounds) Sources vegetation,
combustion CO (carbon monoxide) Sources
combustion, VOC oxidation
Tropospheric ozone precursors
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CONSTRAINING NOx AND REACTIVE VOC EMISSIONS
USING SOLAR BACKSCATTER MEASUREMENTSOF
TROPOSPHERIC NO2 AND FORMALDEHYDE (HCHO)
GOME 320x40 km2 SCIAMACHY 60x30 km2 OMI 24x13
km2
Tropospheric NO2 column ENOx Tropospheric HCHO
column EVOC
2 km
hn (420 nm)
hn (340 nm)
BOUNDARY LAYER
NO2
NO
HCHO
OH
CO
hours
O3, RO2
hours
VOC
1 day
HNO3
Emission
Emission
Deposition
VOLATILE ORGANIC COMPOUNDS (VOC)
NITROGEN OXIDES (NOx)
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TROPOSPHERIC NO2 FROM OMI CONSTRAINT ON NOx
SOURCES
October 2004
K. Folkert Boersma (Harvard)
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TROPOSPHERIC NO2 FROM OMI ZOOM ON U.S. AND MEXICO
MILAGRO campaign, March 2006
K. Folkert Boersma (Harvard)
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1996-2005 TREND IN NOx EMISSIONS SEEN FROM SPACE
Van der A et al., in prep.
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FORMALDEHYDE COLUMNS MEASURED BY GOME (JULY 1996)
2.5x1016 molecules cm-2
2
1.5
1
detection limit
0.5
South Atlantic Anomaly (disregard)
0
-0.5
High HCHO regions reflect VOC emissions from
fires, biosphere, human activity
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FORMALDEHYDE COLUMNS FROM OMI OVER U.S. (July
2005) biogenic isoprene is the principal
reactive VOC
GEOS-Chem chemical transport model with best
prior estimates of VOC emissions
OMI
Dylan B. Millet (Harvard) and Thomas Kurosu
(Harvard-SAO)
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SEASONALVARIATION OF GOME FORMALDEHYDE COLUMNS
reflects seasonal variation of biogenic isoprene
emissions
GOME GEOS-Chem (GEIA)
GOME GEOS-Chem (GEIA)
JUL
MAR
AUG
APR
SEP
MAY
JUN
OCT
Abbot et al. 2003
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TROPOSPHERIC OZONE OBSERVED FROM SPACE
IR emission measurement from TES
UV backscatter measurement from GOME
GOME JJA 1997 tropospheric columns (Dobson Units)
Liu et al., 2006
Is there a summer maximum over the Middle East?
GEOS-Chem model maximum Li et al., GRL
2001 Is it real?
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TES ozone and CO observations in July 2005 at 618
hPa
North America
Asia
TES observations of ozone-CO correlations can
test CTM simulations of ozone continental outflow


Zhang et al., 2006
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USING ADJOINTS OF CHEMICAL TRANSPORT MODELS TO
INVERT FOR EMISSIONS WITH HIGH RESOLUTION
MOPITT daily CO columns (Mar-Apr 2001)
Correction to model sources of CO
Inverse of atmospheric model
A priori emissions from Streets et al. 2003
and Heald et al. 2003
Monika Kopacz, Harvard
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OBSERVING CO2 FROM SPACEOrbiting Carbon
Observatory (OCO) to be launched in 2008
Polar-orbiting solar backscatter instrument,
measures CO2 absorption at 1.61 and 2.06 mm, O2
absorption (surface pressure) at 0.76 mm global
mapping of CO2 column mixing ratio with 0.3
precision
Pressure (hPa)
OCO will provide powerful constraints on regional
carbon fluxes
Averaging kernel
(sensitivity)
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LOOKING TOWARD THE FUTURE GEOSTATIONARY ORBIT

• UV-IR sensors would provide continuous
  high-resolution mapping (1 km)
• on continental scale boon for air quality
  monitoring and forecasting

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LAGRANGE POINTS MISSION CONCEPTS
L2 nighttime Earth continuous solar occultation
measurements

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

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PROPOSED L-1 MISSION TO NASA(Janus)

• 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

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
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OBSERVING SYSTEM FOR ATMOSPHERIC COMPOSITIONMUST
INTEGRATE SATELLITES, IN SITU MEASUREMENTS, AND
MODELS
NEW KNOWLEDGE
Satellites
Air quality monitoring forecasting
Source quantification, policing of
environ- mental agreements
Chemical transport models
Long-range transport
Biogeochemical cycling
Climate forcing
Surface monitors
Aircraft, lidar
Weather forecasting