TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite...

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TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1 , M. Van Roozendael 1 , R. Van Der A 2 , H. Eskes 2 . 1: BIRA-IASB, 2: KNMI

Transcript of TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite...

Page 1: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Tropospheric Formaldehyde (CH2O) from Satellite Observations.

Isabelle De Smedt1, M. Van Roozendael1,R. Van Der A2, H. Eskes2.

1: BIRA-IASB, 2: KNMI

Page 2: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Formaldehyde in the troposphere

• NOx/VOCs ratio determines the production of ozone in the troposphere. Satellite observation of NO2 and CH2O support air quality control.

• CH2O is one of the most abundant carbonyl compounds and a central component of VOCs oxidation. Its observation can help to constrain VOC emissions.

• Sources: - Methane oxidation (background)

- Biogenic VOCs oxidation (isoprene) - Anthropogenic hydrocarbon oxidation - Biomass burning (as first and secondary product)

• Sinks : Oxidation by OH radical and Photolysis - Major source of CO

- Production of HO2

• CH2O has a spectral signature of absorption in the near UV and can therefore been retrieved from satellite observations with the DOAS technique.

Page 3: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

The TEMIS Project

• Objective within the TEMIS project: improve the quality of CH2O retrieval from satellite and provide a consistent long term series of CH2O observation combining different instruments.

• Two satellite instruments:1. GOME on ERS2:

– launched in 1995. Full coverage until June 2003.

– 320 x 40 km2 ground pixel

– sun-synchronous orbit, 10:30

– global coverage in 3 days

2. SCIAMACHY on ENVISAT:– launched in 2002.

– 60 x 30 km2 ground pixel

– sun-synchronous orbit, 10:00

– global coverage in 6 days

Page 4: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

• DOAS technique in two independent steps: 1. Fit of slant columns (absorption

along the satellite viewing path). SCD are retrieved with the WINDOAS software.

2. Determination of air mass factors to obtain vertical columns. AMF are computed with radiative transfer calculations to model scattering in the troposphere and CH2O profile shape from 3D-CTM.

The TEMIS Project

• Tropospheric CH2O is a joined product between BIRA-IASB and KNMI.

Page 5: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

1: CH2O Slant Columns

• In UV, main absorbers are Ozone and Ring effect.

• CH2O optical depth smaller.

Optical densities: SC.σ(λ)

SC O3 = 2x1019 mol/cm²SC NO2 = 5x1016

SC CH2O = 1x1016

SC BrO = 1x1014

• Fit very sensitive to: •S/N ratio•Other molecules absorption•Fitting window•DOAS corrections

Page 6: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

1: CH2O Slant Columns

• DOAS settings have been optimized in order to obtain a consistent time series combining the two instruments.

• Particularly, the fitting windows has been shifted more in the UV to avoid a spectral artefact in SCIAMACHY spectra.

• I0: radiance selected daily in the Pacific Ocean.

• Reference sector correction based on the background of CH2O in the Pacific only due to CH4 oxidation.

p

ppi

ii aSC

I

I

)('

)(ln

)(ln)(

0

Page 7: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

• Compared to first version of the TEMIS GOME CH2O product, SCD have been analysed in a new fitting window (328.5-346 nm).

• For GOME: Reduction of the background noise and several artefacts above desert regions.

• For SCIA: Allows to retrieve CH2O consistent with GOME.

GOME CH2O SCD [x1015 mol/cm²]1997-2002

1: CH2O Slant Columns

Page 8: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

atm

dzmonthlonglatzSAltAlbCTCFangleszWFAMF ).,,,().,,,,,(

2: AMF Determination

• Scattering by clouds and air particles makes the AMF dependant on the vertical distribution of the molecule. 

• Scattering properties of the atmosphere modelled with a RTM (Disort). WF depend on observation angles, cloud properties, albedo and ground Altitude.

• Cloud Correction based on the independent pixel approximation and on the FRESCO product.

• Vertical distribution of CH2O is taken from the tropospheric 3D-CTM IMAGES. The profile shape S(z) is the normalized profile: S(z) = P(z)/∫P(z).  

WF

Profile as seen by GOME

• Intex-A campaign• Jul.2004

NCARURI

Page 9: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

CH2O Vertical Columns

Jan.2003 – Jun.2007

• GOME CH2O VC averaged over 7 years (from 1996 to 2002) and the SCIAMACHY CH2O VC over the next 4 years and half (from 2003 to mid 2007).

• The general agreement between both instruments allows the generation of a combined long-term time series of CH2O vertical columns covering a full decade from 1997 until 2006.

Apr.1996 – Dec.2001

Page 10: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

GOME – SCIAMACHY CH2O VCD [x1016 mol/cm²]Jan. – Jun. 2003

CH2O Vertical Columns

Over the 6 first months of 2003:• General agreement within

7.5x1015 mol/cm².• SCIA is higher than GOME

from 40° in latitudes N and S.• South Atlantic Anomaly effect

is different.

Page 11: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

CH2O Vertical Columns: America

• Good agreement over the six first months• Stronger seasonal variability with SCIA.

• Very good agreement in South America• Stronger SAA effect with SCIA

Page 12: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

CH2O Vertical Columns: Asia

• Good agreement over the six first months, SCIA a bit lower.

• Much stronger seasonal variability with SCIA.

• Very good agreement in biomass burning regions.

Page 13: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

CH2O Vertical Columns: Africa

• Very good overall agreement in Africa.

Page 14: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Special Event: Greek Fires this Summer

CH2O as measured by SCIA on 26 August 2007 superimposed over an image made by MODIS. Due to the strong north-easterly wind the smoke from the forest fires is blown all the way to the coast of Lybia.

Page 15: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Total VCD Error Evaluation

² ( )² ² ( )² ² ( )² ²

²1 1² ( )² ² ²

² ² ²

O

rand

syst O

VC SC AMF VCO

SC

SC AMF VC

VC VC VC

SC AMF VC

SC

AMF N AMF AMF

OO O

SC SC SCVC VC VC

AMF AMF

• Vertical columns calculated from the slant columns (SC), air mass factors (AMF) and a zonal correction above Pacific Ocean (SCO and VCO): 

• As the determination of the SC, AMF and VCO are independent, the total error on the tropospheric vertical column can be expressed as: 

• σSC: error on the SC. Can be separated into its random and systematic part.

• σAMF : error on the AMF evaluation.

• σVC0 : error on the background correction above Pacific Ocean. 

Page 16: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Global Error Budget

• Total Error around 25%.• At low and mid latitudes,

AMF error dominates with the main contribution from clouds and profile shape uncertainties.

• At higher latitudes, SC error dominates because of higher Ozone concentrations.

• Monthly average allows to reduce SC random error. 

VCoAMFsystSCrand

VCD AMF

SC

AMFNAMF²²)²

²(²

²

²

Page 17: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Users

• Modellers community:– IMAGES (J-F Muller and J. Stavrakou, BIRA-IASB, Brussels):

current user, paper in preparation.– CHIMERE (G. Dufour, LISA, Paris): future user, data provided.– GEOS-CHEM (P. Palmer, Tropospheric Chemistry Earth

Observation Modelling and Measurement Group, University of Edinburgh): other possible user.

• National and regional environmental protection agencies:– Europe: UBA-Austria, EMPA Switzerland and LANUV

Northrhine-Westfalia: users within Promote.– China: National Satellite Meteorological Centre NSMC (Peng

Zhang), Institute of Atmospheric Physics, CAS IAP-CAS (Pucai Wang): Contacts in China through the AMFIC project, can help to find users there.

Page 18: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Conclusions and Outlook

• On the TEMIS website, you will find:

– Daily, monthly and yearly maps for GOME and SCIAMACHY.

– Data files with averaging kernels and error estimation for each satellite pixel.

• The dataset will be regularly extended with fresh SCIA data.

• The analysis of GOME-2 data will start within the next months. The global coverage in 1,5 day should allow to reduce the noise in the results.

• Consistency between the platforms needs to be evaluated regularly (changes in time) and validated with ground-based measurements that become more and more available for CH2O.

Page 19: TEMIS user workshop, Frascati, 8-9 October 2007 Tropospheric Formaldehyde (CH 2 O) from Satellite Observations. Isabelle De Smedt 1, M. Van Roozendael.

TEMIS user workshop, Frascati, 8-9 October 2007

Conclusions and Outlook

• The quality and the consistency of the data is very important to be able to detect possible trends in emissions.

• A derived product based on inverse modelling could be developed within TEMIS to provide constraints on VOC emissions. Possibilities of more users working on emission inventories (GFED, MEGAN).