Requirements for monitoring methane from space: What would ...€¦ · bhd bik bkt bmw bme brz brw...
Transcript of Requirements for monitoring methane from space: What would ...€¦ · bhd bik bkt bmw bme brz brw...
Requirements for monitoring methane from space:
What would we need to separate processes?
Julia Marshall, Tonatiuh Nuñez Ramirez The Climate Needs Space, Toulouse, 10-11 October, 2017
Max Planck Institutefor Biogeochemistry
The importance of methane
• second-most important greenhouse gas that is modified by human activities
IPCC, AR5, 2013
The importance of methane
• second-most important greenhouse gas that is modified by human activities
IPCC, AR5, 2013
Similar to the problem of CO2 in some ways…
• also tackled by top-down or inverse modelling
• also involves combined signals of anthropogenic and biogenic fluxes
• also requires a challengingly high measurement precision and accuracy
GHG-CCI URD v2.1, Buchwitz et al., 2016
Current measurement requirements
GHG-CCI URD v2.1, Buchwitz et al., 2016
Current measurement requirements
1 ppm/~400 ppm = .25%
GHG-CCI URD v2.1, Buchwitz et al., 2016
Current measurement requirements
1 ppm/~400 ppm = .25%
9 ppb/~1800 ppb = .5%
GHG-CCI URD v2.1, Buchwitz et al., 2016
Current measurement requirements
1 ppm/~400 ppm = .25%
9 ppb/~1800 ppb = .5%
0.2 ppm/~400 ppm = .05%
GHG-CCI URD v2.1, Buchwitz et al., 2016
Current measurement requirements
1 ppm/~400 ppm = .25%
9 ppb/~1800 ppb = .5%
0.2 ppm/~400 ppm = .05%
1 ppb/~1800 ppb ≈ .05%
Current measurement requirements
• 10 ppb “required measurement uncertainty” (2-σ value)
• 7 ppb/decade stability requirement
High precision requirements are a function of the small gradients we are after
In all cases:
• truly random error (noise) can be dealt with
• systematic errors (bias) result in erroneous flux estimation
In all cases:
• truly random error (noise) can be dealt with
• systematic errors (bias) result in erroneous flux estimation
Requirement: Very low bias, reasonable precision
Difference to CO2: Significant uncertainties in all contributing processes
• generally easier to solve for the total CH4 budget, and divide into processes based on bottom-up share per pixel
• separating the processes directly introduces more unknowns, and requires more constraints
from synthesis of Saunois et al., ESSD, 2016
Another difference to CO2: Enigmatic recent changes in the growth rate
Another difference to CO2: Enigmatic recent changes in the growth rate
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Another difference to CO2: Enigmatic recent changes in the growth rate
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Another difference to CO2: Enigmatic recent changes in the growth rate
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Separation of processes• we have information on the spatial distribution of
processes based on our bottom-up inventories and process models
Saunois et al., 2016
The (somewhat) current observation network●
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The (somewhat) current observation network
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The (somewhat) current observation network
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BSC
CBAC
CFA
CGO
CHL
CHR
CMO COI
CPT
CARVE
CRI
CRZ
CVO
CYA
DEM
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EGB
EIC
ESPETL
FIK
FSD
GLH
GMI
GOZ
GPA
GSN
HAT
HBA
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ICE IGR
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K34/TT34
KAS
KEY
KRS
KUM
KZD KZM
LAU
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LLN
LMP
LPOL/K
MAA
MBC
MEX
MHD
MID
MKN
MLOMNM
MQA
NAT
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NMY
NWR
NZL
OPW X
PAL
PBL
PDM
PON
PRS
PSA
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SEY
SGI
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SHM
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SMO
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STMSUM
SUV
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TDF
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TKB
TLL
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UTAUUM
VGNVKV
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WSA
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YON
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ZOTTO
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BIK
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IZOJPLJPL
K
SGP
LAULAU
OLEF
CAL
RUN
SAG
SKY
WLG
ARH
B
EUK
IZO
J
KIR
LAU
MLO
RUN
THU
TOT Z
BSL
BSLBSL
POC
POC
POC
POCSCS
WPC
WPC
AIA
AOA
AFL
FTLMAN
PIP
RBASAN
SRG
TAB
DRP
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Latit
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●●●●●●●● ●●●●●●●●Aircraft CARIBIC CONTRAIL GOSAT Ground station Ship transect Total Column UCI network
Requirement: Well-calibrated long-term surface measurements of methane
Satellite measurements of methane with sensitivity in the lower troposphere up to now:
• SCIAMACHY on Envisat (2002-2012, sensor degradation after 2005)
• TANSO-FTS on GOSAT (2009-present
A note about thermal infrared sounders:
• AIRS, IASI, and TES offer long records with good spatial coverage
• the sensitivity of the thermal infrared sounders to the upper troposphere limits their application in flux inversion
Worden et al., AMT, 2015
SCIAMACHY: SCanning Imaging Absorption Spectrometer for Atmospheric CHartographY
• despite poor precision, systematic errors, and sensor degradation, it provided new insight into methane fluxes (e.g. Bergamaschi et al., 2009 and 2013; Bousquet et al., 2011; Houweling et al., 2014)
• could detect hotspot emission regions with sufficient averaging…
data from 2004, 0.5˚ binning, Buchwitz et al., ACP, 2017
GOSAT offers better precision, but poorer coverage
GOSAT offers better precision, but poorer coverage
“full physics” retrieval has lots of gaps in regions with
high cloud cover, aerosol load, andsolar zenith angles
GOSAT offers better precision, but poorer coverage
so-called “proxy” retrieval solves for the ratio of XCH4:XCO2, and
multiplies it by a (better known) modelled XCO2 value
“full physics” retrieval has lots of gaps in regions with
high cloud cover, aerosol load, andsolar zenith angles
Sentinel-5P (launching on Friday!) will provide a huge increase in coverage
being encapsulated into its fairings on October 3, 2017(Credits: ESA–Stephane Corvaja, 2017)
Sentinel-5P
• 7 km x 7 km spatial resolution (compare to 30 km x 60 km for SCIAMACHY, 10 km diameter for GOSAT)
• 2600 km swath
• daily global coverage (minus the clouds…)
• also measuring CO, O3, NO2, SO2 (but not CO2)
What this means for a simulated 500 kTCH4 point source:
courtesy H. Bovensmann, IUP-Bremen
What this means for a simulated 500 kTCH4 point source:
courtesy H. Bovensmann, IUP-Bremen
Requirement: High spatial resolution for detection of spatial patterns of fluxes
Difficulties can still arise when fluxes are co-located
Other tracers provide us with information about these processes:
Ethane, C2H6
• most abundant atmospheric hydrocarbon after methane
• primary sources are fossil fuels, biomass burning, and biofuels
Simpson et al., Nature, 2012
What ethane tells us• comparison of
short-lived ethane to methane growth rate suggests at least 30-70% of the slow-down was due to reduced fugitive emissions
Simpson et al., Nature, 2012
What ethane tells us
• ground-based total- column measurements from northern hemisphere and southern hemisphere suggest increase after 2007 was largely due to fossil fuel emissions increase
Hausmann et al., ACP, 2016
Other tracers provide us with further information about these processes:
stable isotopologue δ13CH4
• expresses ratio of 13C/12C-ratio in atmospheric CH4 in δ-notation relative to VPDB-standard
• different source types have distinct signatures
• there is significant uncertainty on these signatures, however
Schwietzke et al., Nature, 2016
Other tracers provide us with further information about these processes:
stable isotopologue δ13CH4
• expresses ratio of 13C/12C-ratio in atmospheric CH4 in δ-notation relative to VPDB-standard
• different source types have distinct signatures
• there is significant uncertainty on these signatures, however
Schwietzke et al., Nature, 2016
very depleted microbial signature
• one interpretation of these data (in a one-box model) suggests that the recent increase is driven by (depleted) microbial sources
• this is attributed to agriculture
Schaefer et al., Science, 2016
Nisbet et al., GBC, 2016
• the same data were simultaneously published as being indicative of climate-related increases in tropical wetland emissions
• a cow’s stomach is a bit like a wetland, isotopically speaking
• while others argue for a redistribution of the budget, and a decrease in fossil sources along with a microbial increase, contrary to the ethane data
Schwietzke et al., Nature, 2016
Ideally these pieces of information could be combined to provide a consistent answer…
Why is this so unclear?
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• these supporting measurements are sparse, especially in the tropics
• uncertainties on the regional distribution of source signatures remains
δ13CH4
C2H6
Why is this so unclear?
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• these supporting measurements are sparse, especially in the tropics
• uncertainties on the regional distribution of source signatures remains
δ13CH4
C2H6
Requirement: globally distributed sampling of related tracers
But also methane measurements are sparse in some regions
• persistent tropical clouds make satellite measurements difficult during much of the year
• requirement of sunlight limits high latitude measurements seasonally
• here an active lidar sensor (like MERLIN) with a footprint of only ~100 m and its own radiation source can provide much-needed low-bias data
Unknowns in the Arctic: wetland emissions during the zero curtain (and beyond)
Mastepanov et al., Nature, 2008
MERLIN: Polar-orbiting active sensor will offer data at all latitudes over the whole year
Ehret et al., Remote Sensing, 2017 (accepted)
Satellite/Instrument XCO2 XCH4 IFOV ‘12 ‘13 ‘14 ‘15 ‘16 ‘17 ‘18 ‘19 ‘20 ‘21 ‘22 ‘23 ‘24 ‘25
Envisat/SCIAMACHY ✓ ✓ 30 km x 60 km
GOSAT/TANSO-FTS ✓ ✓ 10.5 km (D)
OCO-2 ✓ 1.25 km x 2.26 km
TanSat ✓ 1 km x 2 km
Sentinel-5P/TROPOMI ✓ 7 km x 7 km
Gao Fen-5 ✓ ✓ 10 km (D)
GOSAT-2/TANSO-FTS ✓ ✓ 9.7 km (D)
FengYun-3D ✓ ✓ 10 km (D)
OCO-3 ✓ ~2 km x 2 km
MicroCarb ✓ 4.5 km x 9 km
MERLIN ✓ 100 m x ~50 km
Sentinel-5 (a, b, c) ✓ ✓ 7 km x 7 km
GeoCARB ✓ ✓ ~10 km x 10 km
Sentinel-7 ✓ ✓ ~2 km x 2 km
year
The future from space looks promising…
Satellite/Instrument XCO2 XCH4 IFOV ‘12 ‘13 ‘14 ‘15 ‘16 ‘17 ‘18 ‘19 ‘20 ‘21 ‘22 ‘23 ‘24 ‘25
Envisat/SCIAMACHY ✓ ✓ 30 km x 60 km
GOSAT/TANSO-FTS ✓ ✓ 10.5 km (D)
OCO-2 ✓ 1.25 km x 2.26 km
TanSat ✓ 1 km x 2 km
Sentinel-5P/TROPOMI ✓ 7 km x 7 km
Gao Fen-5 ✓ ✓ 10 km (D)
GOSAT-2/TANSO-FTS ✓ ✓ 9.7 km (D)
FengYun-3D ✓ ✓ 10 km (D)
OCO-3 ✓ ~2 km x 2 km
MicroCarb ✓ 4.5 km x 9 km
MERLIN ✓ 100 m x ~50 km
Sentinel-5 (a, b, c) ✓ ✓ 7 km x 7 km
GeoCARB ✓ ✓ ~10 km x 10 km
Sentinel-7 ✓ ✓ ~2 km x 2 km
year
The future from space looks promising…
Provided the following requirements are met:
• satellite data with low bias and reasonable precision
• maintenance of well-calibrated surface measurements
• high spatial resolution for imaging/separation of flux patterns
• active sensors for low bias coverage at high latitudes and in cloudy regions
• expansion of supplemental tracer measurements (ethane, isotopes)
• improvement of stratospheric representation in models
• a proxy for the hydroxy radical sink going forward( )