CH 4 TOTAL COLUMNS FROM SCIAMACHY – COMPARISON WITH ATMOSPHERIC MODELS

ICDC7, Boulder, 26-30 September 2005

CH4 TOTAL COLUMNS FROM SCIAMACHY –

COMPARISON WITH ATMOSPHERIC MODELS

P. Bergamaschi1, C. Frankenberg2, J.F. Meirink3, M. Krol1, F. Dentener1, M. van Weele3,T. Wagner2, U. Platt2, S. Koerner4, M. Heimann4,

1European Commission Joint Research Centre, Institute for Environment and Sustainability, Ispra, Italy2Institute for Environmental Physics, University of Heidelberg, Heidelberg, Germany3Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands4Max Planck Institute for Biogeochemistry, Jena, Germany


SCIAMACHY

absorption spectra of solar radiation (near-IR)

-> high sensitivity also towards the surface

Main challenge:

Target precision / accuray ~ 1%


SCIAMACHY - validation

ground based FTIR (total column measurements)

NDSC network

- very few stations (~11) only; no coverage of tropical source regions

- FTIR precision (~3%), accuracy (~7%) [Dils et al., 2005]

comparison with other satellites

currently no other CH4 retrievals available

(except some exploratory retrievals from IMG/ADEOS (1997)

inverse modelling

using high precision / accuracy surface insitu / flask measurements (CH4 ~ 0.1%)

-> global 3D CH4 fields

alternative approach:


model - validation

validation of models (and bottom-up emission inventories)

in particular over source regions which are not well sampled by the surface measurements

Final objective:

Better quantification of CH4 emissions

opposite view:


TM5 model

TM5 model – atmospheric zoom model

• offline atmospheric transport model

• meteo from ECMWF

• global simulation 3o x 2o

• zooming 1o x 1o (North America, South America, Europe, Africa, Asia, Australia)

• http://www.phys.uu.nl/~tm5/

• [Krol et al., 2005]


TM5 simulationsinversion based on groundbased monitoring sites

synthesis inversion optimizing:

- monthly emissions

- 11 source categories

- 7 global regions for wetlands

- 5 global regions for biomass burning

ground based background monitoring sites (NOAA/CMDL)


TM5 inverse simulationsexamples for some monitoring sites

simulation of global CH4 consistent with surface monitoring sites (background sites)

01 Jan 31 Dec


SCIAMACHY vs. TM5 - global

2003 average

column averaged CH4 [ppb]

TM5

SCIA



2003 average


TM5

SCIA

N-S gradient ~100 ppb

consistent between SCIA and TM5



2003 average


TM5

SCIA

Enhanced CH4 over SouthEast Asia and tropical regions (S.America, Africa)


SCIAMACHY vs. TM5 - Asia 04-06 2003

TM5

SCIA



TM5

SCIA


SCIAMACHY vs. TM5 - South America 01-03 2003

TM5

SCIA



TM5

SCIA


South America 01-03 2003 JK

CH4 emission from wetlands: J. Kaplan [2005]

spatial distribution of wetlands based on GLC2000

TM5

SCIA


South America 01-03 2003 BW

CH4 emission from wetlands: Walter et al. [2001]

spatial distribution of wetlands based on [Matthews and Fung, 1987]

TM5

SCIA


SCIAMACHY vs. TM5: global std, bias

std

bias

daily SCIA retrievals vs. TM5 (global over land)


Conclusions

• SCIAMACHY provides view on global CH4 distribution

• Enhanced CH4 over SouthEast Asia, and tropical regions of South America and Africa (CH4 up to ~70 ppb)

• Comparison with inverse simulations, optimized towards insitu observations:

• Background regions: reference for validation of SCIAMACHY retrievals

• Source regions: Different model scenarios yield significantly different CH4 distributions -> rather check of consistency than strict validation

• major uncertainty: CH4 emissions from wetlands

• overall std: 23.6 ppb (1.4%) - upper estimate of SCIA precision

• potential (seasonal) bias (in particular over Australia (~20 ppb))

• average N-S gradient (~100 ppb) consistent between SCIAMACHY and TM5


Thank you !


Supporting Material


SCIAMACHY / ENVISAT

SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY)

SCIAMACHY on ENVISAT

altitude: 800 km

14 orbits per day

full global coverage: every 6 days

CH4: 1563-1585 nm

CO2: 1631-1670 nm

(O2: 760 nm)


SCIAMACHY VCD->VMR

variability of total columns:

CO2 ~ 1/3 CH4

Conversion

vertical column densities (V) [molec / cm2]

-> column averaged mixing ratios (VMR) [ppb]

use of CO2 instead of O2 for determination of total vertical column of dry air [Frankenberg et al., Science, 2005]

-> very similar light path distribution (scattering)

CO2 VMR from TM3

column averaged CH4 mixing ratio [ppb]


SCIAMACHY - averaging kernels

[Frankenberg et al., 2005]


SCIAMACHY vs. TM5 - global (incl. ocean)


emission inventories for TM5 simulations

coal IIASA / EDGAR V3.2oil and gas IIASA / EDGAR V3.2enteric fermentation IIASA / EDGAR V3.2rice GISS [Matthews et al., 1991]biomass burning [van der Werf et al., 2004]waste IIASA / EDGAR V3.2wetlands [Kaplan, 2005]

[Walter et al., 2000]wild animals GISS [Fung et al., 1991]termites GISS [Fung et al., 1991]ocean [Houweling et al., 1999]soil sink GISS [Fung et al., 1991]

bottom-up emission inventories used as priori emissions for inverse TM5 simulations:

CH 4 TOTAL COLUMNS FROM SCIAMACHY – COMPARISON WITH ATMOSPHERIC MODELS

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