greenhouse gas monitoring by lidar in space
TRANSCRIPT
PHF XVI CLRC Long Beach, CA, June 20-23, 2011 1
Greenhouse Gas Monitoring by Lidar in SpaceGreenhouse Gas Monitoring by Lidar in SpaceMERLIN Initiative for MethaneMERLIN Initiative for Methane
Pierre H. FlamantPierre H. Flamant11 & Gerhard Ehret & Gerhard Ehret22
MERLIN Scientific Advisory Group (CNES-DLR)A-SCOPE Scientific Advisory Group (ESA)
1Laboratoire de Métérologie Dynamique, École Polytechnique, Palaiseau, France2Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen, Germany
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Dial activity on GHG i.e. CO2 and CH4, get started in early 2000 We, scientits, gained experience by our (leading) contribution to
various studies funded by ESA We had a phase “0” study by industry for the CO2 mission A-
SCOPE More recently in 2010 the EXCALIBUR proposal for CO2
mission was submitted in response to call for ideas for ESA EE-8 mission opportunity
Today, we built on this common long term expertise to conduct theFranco-German climate mission MERLIN for CH4
FORWORDFORWORD
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Needs on GHG for Climate Change IssueNeeds on GHG for Climate Change Issue
Better understanding of climate change direction in near future isbased on assessment of carbon sources and sinks strengths withtime and locations and atmospheric GHG fluxes
3 main Greenhouse Gases: water vapor (H2O), carbon dioxide(CO2), methane (CH4)
Monthly GHG fluxes at global scales call for accurate and evenlydistributed GHG concentration that in turn call for remote sensingtechniques (passive and active) for flexibility to overcome inherentsparse and limited deployment of surface network, TCCON sitesand airborne in situ probes and flask measurements
Passive missions already in space (GOSAT/JAXA), ready to go(OCO-2/NASA), or in preparation (CarbonSat/ESA EE-8,MiniCarb/CNES)
Active remote sensing technique i.e. DiAL technique in spacealready studied: A-SCOPE/ESA (phase 0) and MERLIN/CNES-DLR(phase A)
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High potential ofhazardousness⇒ methanisationof atmosphere
• Sources ?. « C »cycle,radiationbudget
. Low variabilityaround 1,7 ppmvBUT …. ± 2 %
. ABL
. Troposphere
. UTLS, lowstratosphere
. Natural &Anthropogenic. Highlyreactive (withOH)
MethaneCH4
Slow continuousraising ⇒temperatureincrease
. Sinks?
. « C »cycle,radiationbudget
. Low variabilityaround 380 ppmv. ± 1 ppmv (0,3 %)
. ABL
. Troposphere
. UTLS, lowstratosphere
. Anthropogenic
. Passive
. Diurnal cycle
CarbondioxideCO2
Indirect: rain &fresh wateravailability, …
. Primaryvariable. Water cycle,radiation buget
≈ 0 to 20 g/Kg. Large variabilityin space & time. ± 10 %
. ABL,
. Troposphere
. UTLS, lowstratosphere
. Natural
. Weaklyreactive. Gas, liquid,solid
Watervapor H2O
Potential climatichazardousness
Importance inMeteorology
Climate
ConcentrationPrecision
Verticaldistribution
Origine &Reactivity
Specie
a priori : GHG measurements from space assume broad representativity distribution inspace and time ⇒ sampling the atmosphere at random is adequate
MOTIVATIONS & OBJECTIVESMOTIVATIONS & OBJECTIVES
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Lidar signal strength (W)• Laser energy per pulse (E)• Receiver collecting area (A)• Photo detector efficiency (q <1), detection noise, inherent electronic
noise (NEP), background light, speckles effect• Ideally : signal detection noise only• The photodetector play a key role !!!• Target reflectivity ⇒ lidar signal strength ⇒ SNRWall plug efficiency. 2 effects on output energy and duty cycle,
dimensioning of cooling system
Time allocated for one measurement (t) : Vsat = 7 km/s ⇒ t =7/14 s⇒ horizontal resolution ≈ 50/100 km
Number of independent samples N to reduce the random error ⇒ √Nwith N= F x t, where F is the pulse pair repetition rate
Detailed spectroscopy of few absorption lines
Key elements for a GHG Mission
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• Pulsed emission for accurate ranging (3 m) and preferred shortpulse duration
• Tunable laser at at least 2 wavelengths λabs (λon) and λref (λoff)in less than a 1ms for efficient pair correlation
• Accurate spectral tuning. Stable operation and high spectralstability at λon ⇒ absorption cross section Δσ ⇒ bias.
• High spectral purity at λon for low bias. Spectral purity isdictated by bias
• Several λabs according to range of concentration• Several λref according to spectral dependence of scattering
properties (in particular NIR)• Energy per pulse ⇒ SNR (in DD) ⇒ random error• SLM emission and good M2
• PRF for accumulation of independent samples in a given time‘or horizontal distance ⇒ measurement accuracy
LaserLaser Characteristic Characteristic for for DiAL DiAL ApplicationApplication
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All solid pulsed laser ⇒ several solutions
Lasers for COLasers for CO22 & CH & CH44 DiALsDiALs
MissionsDiALs airborneDiALs on groundLaser
EXCALIBUR-COWI 2-µm (LMD)(see F. LeMounier)- NASA-LaRC 2µm
Diodes laser ⇒ 1st Tm fiberlaser ⇒ 2nd Ho laser in freespace cavity
2 µm Qinetiq/ESADiodes laser ⇒ fiber laser
A-SCOPEMERLINMERLIN
CHARM-F (DLR)1,57 et 1,64 µminjection seeded
PULSNIR 2 µm« DROPO »ONERA/ESA
Diodes laser ⇒ 1st laser ⇒OPO+ APO(s)
A-SCOPENASA LaRC 2µmDiodes laser ⇒ laser
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DiAL DiAL TechniquesTechniques
DiALpulsed laserlarge E A q
Range resolved
IPDAPulsed lasersmall E A q
ColumnWeighting Fct
Laser (E)Telescope (A)Detector (q)
Laser, TelescopeDetector
Laser, Telescope,Detector
Molecules &particlesβ(x,z) . Δz
Surface ρ/π
Retroreflector
Laser
TelescopeDetector
Nadir Nadir
Zenith
WALES (ESA)A-SCOPE (ESA)
MERLIN (CNES/DLR)
ACCURATE (ESA)
ADEOS (JAXA)
Limb
IPDAPulsed lasersmall E A q
ColumnWeighting
Fct
IPDADiode laser
small E A qUTLS
Weighting Fct
Methodology:Molecular absorption ⇒measurement signatureTarget reflectivities ⇒measurements support
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WALES / ESAWALES / ESA
4 Lidar(s)configurationparaxiale
Télescope(s) ≈ 2 m
4 wavelengths (3On- and 1 Off- inthe 940 nmspectral range
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CH4
CO2
Molecular SpectroscopyMolecular Spectroscopy
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Call for Earth Explorer Core missionLetter of Intent mid 2005Phase « 0 » in 2007-2008 with 5other missionsESA report WP 1313/1 2008UCM in January 2009
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On Range accuracy for surface pressure• 1 hPa corresponds to about 10 m. Sampling at 3 m resolutionWhat acceptable angular fluctuations on LOS pointing to result in
range unknown variation ≤ 3 m?For 600 km orbit• At nadir Δθ≈ 3 mrad• For θo = 1° (X=9 km) and Δθ≈ 0.3 mrad• For θo = 10° (X=88 km) and Δθ≈ 30 µrad
On Beam overlapping at ground• Overlap of On- and Off wavelength beams at surface is critical
for bias for surface with characteristics. It needs to be very goodto results in negligible bias (10-3) on DAOD and XCH4 after 50km accumulation
• How good it needs to be depends on i) surface reflectivitygradient (Δρ(X,Y)) within the beam footprints and ii) beamintensity distribution (linked to laser M2)
Pointing IssuesPointing Issues
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A-SCOPE SAGA-SCOPE SAG
A-SCOPE got excellent review but due to low TRL for some key elementsA-SCOPE was not selected for phase A!
At UCM in Lisbon, January 2009
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“EXCALIEXCALIBURBUR” “EXPERIMENT ON CARBON DIOXIDE (CO2) BY LIDAR FOR
BIOSPHERE AND CLIMATE URGENCY”
IN RESPONSE TO ESA CALL FOR PROPOSALS FOR EARTH EXPLORER
OPPORTUNITY MISSION EE-8
by
Pierre H. FLAMANT
and
Dr. Philippe CIAIS Pr. John DAVID Dr. Kenneth DAVIS
Dr. Gerhard EHRET Dr. Fabien GIBERT Pr. Nicolas GRUBER
Dr. Ir. Sander
HOUWELING
Jason HYON Dr. Xavier MARCADET
Dr. Robert T. MENZIES Pr. Anna M. MICHALAK Dr. Marko SCHOLZE
Dr. Upendra N. SINGH Dr. Jirong YU
ESA Call for idea in 2009 forMission Opportunity EE-8- 100 M euros Budget cape forpayload and dedicated missionground segment- Letter of Intent due Dec. 2009- Full proposal June 2010.
New proposal wrt A-SCOPE- New 2-µm photodetector to bedevelopped in Europe- New 2-µm pulsed lasertransmitter to be provided byNASA
- Excellent review (again) butnot selected late 2010 forphase A
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MERLIN is the Franco-German climatemission initiated in late 2009 for a launch in2014 and for three years of operation.
It is dedicated to atmospheric methane (CH4). Itwill contribute/complement global GHGObserving System (i.e. networks, aircraft,passive missions) through accurate CH4 spatialand temporal distribution, globally.
It is a Micro-Sat class mission with "small" OPOlidar (90 -130 W, 80-100 kg) on the MYRIADEplatform to demonstrate IPDA using an activeinstrument is a powerful technique in space
It will provide weighted CH4 column content innadir direction relying on signal strengthsassociated to surface reflectivity (soils,vegetation, water)
The primary data product will be methane dryair mixing ratio XCH4
CHCH44 & MERLIN Mission Context & MERLIN Mission Context
Artist view of the spacecraft MYRIADE fromCNES carrying the CH4 IPDA lidar instrumentfrom DLR
Mission status
• successful Mission DefinitionReview end of 2010
• Phase A since Jan. 2011
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• A Franco-German Climate initiative was put on the table in 2009 duringone of the regular Franco-German Ministry meeting
• Before that, DLR had already conducted a paper study (CHARM) onsmall CH4 mission, and a proposal (OMÉLIE) has been submitted toCNES in view of a Seminar of Prospective
• Budget: 120 M euros total equally shared between France and Germany• MYRIADE platform to be provided by CNES• OPO Lidar to be provided by DLR• MERLIN project under supervision of a Steering Committee (2 + 2
members from CNES and DLR)• One single integrated Project Team led by CNES• One Merlin Scientific Advisory Group in charge of mission objectives,
User Requirement Document, preparatory studies for trade-off,processing algorithms and products definition
• Phase « 0 » in 2010. First cost estimate (really) too high!• Officially in phase « A » since January 2010, but actually still in an
intermediate phase for cost reduction and so called « descoping »activity to get closer (if not equal or lesser) to the budget cape
MERLIN MERLIN OrganisationOrganisation
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Co-Principal Investigators: Pierre Flamant (1), Gerhard Ehret (2)
Co-Investigators: Philippe Bousquet (3), John P. Burrows (4)Frederic Chevallier (3), Philippe Ciais (3), Cyril Crevoisier (1),Andreas Fix (2), Fabien Gibert (1), Martin Heimann (5), Hans-Wolfgang Hubberten (6), Kathy Law (7), Alexander Löw (11),Martin Wirth (1)
Observers: Jim Abshire (8), Christian Frankenberg (9), SanderHouweling (10), Patrick Jöckel (1), Julia Marshall (5), CatherinePrigent (12), Marko Scholze (13)
Contributors: Christoph Kiemle (1), Mathieu Quatrevalet (1)
MERLIN SAGMERLIN SAG
(7) LATMOS, University Pierre et Marie Curie,Paris, France(8) GSFC, NASA, Greenbelt, USA(9) JPL, NASA, Pasadena, USA(10) IMAU, University of Utrecht, Utrecht, theNetherlands(11) MPI for Meteorology, Hamburg, Germany(12) Observatoire de Paris, France(13) DES, University of Bristol, Bristol, UK
(1) Laboratoire de Météorologie Dynamique, ÉcolePolytechnique, Palaiseau, France(2) Institute for Atmospheric Physics, DLROberpfaffenhofen, Germany(3) LSCE, IPSL, Gif sur Yvette, France(4) IUP, University of Bremen, Germany(5) MPI BGC, Jena, Germany(6) AWI, Potsdam, Germany
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• Measurement of the column-integrated dry-air volume mixingratio of methane XCH4 using the IPDA technique with followingspecifications on XCH4:
Threshold, breakthrough, targetRandom error < 36, 18, 8 ppb
Systematic error: < 3, 2, 1 ppbHorizontal resolution: 50 km
• Global coverage Day/Night including high latitudes in wintertime
• No bias from aerosol and cloud scattering due to range-gatedinstrument operation near the surface
MERLIN ScienceMERLIN Science
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Level 2: column-integrated drymixing ratio i.e. XCH4Weighting function WF usingspectroscopy information
!
XCH4 "
[CH4]WF(p)dp
0
psurf
#
WF(p)dp
0
psurf
#=
DAOD
WF(p)dp
0
psurf
#
Level 1b1: range (R) to scatteringthe surface. Surface height abovegeoid zloc to determine localsurface pressure psurf usinghydrostatic equation
Spin-off product: canopy,surface reflectivity
orbitRLidar
R
zloc, psurf
zNWP, pNWP
Data ProductsData Products
Level 1b2: Differential AbsorptionOptical Depth (DAOD) of CH4
!
DAOD =1
2ln
Soff / Eoff
Son / Eon
"
# $
%
& '
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Sun Lighting & EclipsesSun Lighting & Eclipses
Problem associated to amicrosat and low orbit
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Line selectioncriteria
• sufficient opticaldepth
• low interferencewith other GHG
• low temperaturedependency
• sufficient weight inABL
CH4
H2O
CO2
Selected absorption CH4 LineSelected absorption CH4 Line
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soundingat troughpositionfavorable
!"
" )DAOD(
Selected on-line wavelengthSelected on-line wavelength
• Substantial relaxation of instrumentand platform stability requirement
airOH
air
OH
offon
Mg)T,p(M
M1
)T,p()T,p(
2
2 !!""#
$%%&
'(+
)*)= T)WF(p,
• MERLIN WF enables highmeasurement sensitivity inthe low troposphere
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Global Map of Global Map of Surface Surface Reflectance at 1.64 Reflectance at 1.64 µµmmLand surface:
MODIS 16-d compositefor 4 seasonsJan/Apr/Jul/Oct
Sea surface:
refl. ~ 1/wind
sources:30-yr mean w,Menzies 1998, Hu 2008,Josset 2010.
July C. Kiemle and A. Amediek, DLR
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Preliminary PerformancePreliminary PerformanceInstrument and Auxiliary ParametersInstrument and Auxiliary Parameters
Cal. Device
Linearity
Bgr.
Freq. TXPointing
BWTXSp. Purity
Very small instrument error budget of0.8 ppb which compares to 1ppb/3ppbof the systematic target/threshold errorfor MERLIN
Sensitivity ofInstrument Parameter
Small random error budget ~2.4 ppbdue to uncertainties of meteorologicalparameter (psurf,T,q) which compares to8/36 ppb for the random target/thresholderror for MERLIN
Sensitivity of MeteorologicalParameter
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Substantial error reduction in keyregions with respect to the presentknowledge of CH4-fluxes on regionalscale for July
Preliminary Inverse CH4 Flux Modeling ResultsPreliminary Inverse CH4 Flux Modeling ResultsM. Heimann, J. Marshall, MPI-BGC, Jena
1
pri,xpri,d1T1
post,x CJCJC !!!+=
aggregation of 50 km lidarobservations along track:
calculation of posterior fluxcovariance matrix
Use of TM3 model resolutionof 3hr x 8° x 10° x 9
1-(σpost/σpri)
Assumption• Standard scenario using a priori flux and
flux uncertainty based on Mikaloff-Fletcheret al., 2004 with updated, process based,global totals from IPCC AR4
• Neglecting of- possible biases and error correlations
of observations- Transport model error- "Representation” error
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SummarySummary• The French-German Climate mission MERLIN has successfully passed MDR and
is now further investigated in Phase “A”
• MERLIN is a Micro-SAT mission based on an active OPO optical instrument forthe first time
• Initial results from Phase “0” performance studies are encouraging:
- measurements over land and water surfaces at all latitudes possible
- very small instrument error thanks to soundings in the trough region of theselected methane line
- little impact from uncertainties of the meteorological parameter (T,q,psurf)
- inverse modelling using synthetic MERLIN observations will yieldsignificant error reduction of CH4 fluxes over most of the interestingregions of the globe
• The total efficiency of the laser head remains the largest uncertainty with respectto the final SNR budget of the lidar signals which drives the random errorperformance of MERLIN. A predevelopment model is currently constructed in theLab.