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Aerosol information from the UV-visible spectrometer GOME-2

Piet Stammes, KNMI, De Bilt, The Netherlands

7 November 2012

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Contents

• Importance of aerosols• Aerosol microphysics• Spectral absorption by aerosols• GOME-2 • Absorbing Aerosol Index• First results on Aerosol Height

Acknowledgements to:

Martin de Graaf, Gijs Tilstra, Ping Wang, Olaf Tuinder (KNMI)Eyk Boesche (FUB)Marloes Penning de Vries (MPIC)

3weakevents

strongevents

Smoke and Dust

Amazonian rainforestbiomass burning

Sahel biomass burningand desert dust storms

Desert dustSahara

Bodélé

Libian desert

Saudi Arabian lowlands

Thar desert

Taklamakan desert

Indonesian forest fires

Siberian forest firesin July 2006

Californian forest fires

Canadian and Alaskan forest fires June-July 2004

biomass burningsmoke

Smoke from forest fires

Rice straw burning

biomass burning smoke

more data and information can be found at www.temis.nl

Absorbing Aerosol Index map from SCIAMACHY

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Why are aerosols important?©

IPC

C 2007

ClimateAir quality / Health

Air traffic safety Visibility

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Many aerosol types: chemical compositions,

sizes and shapes

http://alg.umbc.edu/

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Dust aerosols

©nasa earthobservatory

Sahara dust event Size distribution

- Fine mode aerosols: around 0.1 micron

- Coarse mode aerosols: around 1 micronAbsorbing aerosols:• Desert dust• Smoke• Volcanic ash

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Absorption by smoke above clouds

De Graaf et al., JGR, 2012

Observation by SCIAMACHY of absorption spectrum of smoke aerosols.

This absorption leads to heating of the troposphere up to 125 W/m2.

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GOME-2 on Metop

since 2006

• UV-visible-near-IR spectrometer • 4 spectral channels, covering 240 - 790 nm • 0.2-0.4 nm resolution• Polarization Monitoring Devices (PMDs) at 15 bands

• Main products: ozone, NO2, SO2, minor gases• Additional products: aerosols, clouds, surface albedo

http://www.esa.int/esaLP/SEMTTEG23IE_LPmetop_0.html

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Pixel size of GOME-2 w.r.t. other sensors

• GOME(-1) ERS-2

• GOME-2Metop-A+B

• SCIAMACHYEnvisat

• OMI EOS-Aura

40 km

320 km

30 km

60 km

40 km

80 km

13 km

24 km Along track

40 km

10 km

GOME-2 PMD

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Absorbing Aerosol Index (AAI) Definition:

where the surface albedo A for the Rayleigh atmosphere simulations is such that:

A is assumed to be wavelength independent:

A340 = A380

Rayleigh

380

34010

meas

380

34010 loglog100R

R

R

Rr

)(Rayleigh380

meas380 ARR

The residue represents the observed 340/380 nm colour as compared to the pure Rayleigh colour (OMI: 354/388 nm)

residue

AAI is the positive part of the residue

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Reflectance at TOA with absorbing aerosols

Doubling-Adding KNMIRadiative Transfer Model

Solar zenith angle = 30°Viewing zenith angle = 0°Surface albedo = 5%

Absorbing aerosols:altitude = 3-4 kmoptical thickness = 2single scattering albedo0= 0.75

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To match the reflectance in the absorbing aerosol atmosphere at 380 nm , the surface albedo is decreased in the Rayleigh atmosphere:

Rayleigh atmosphereSurface albedo = 0.6%

Reflectance at TOA with absorbing aerosolsand matched Rayleigh reflectance

As

Match at reference wavelength

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Reflectance at TOA with absorbing aerosolsand matched Rayleigh reflectance

The curves don’t match at 340 nm:

Absorbing aerosols create a positive residue.

Residue

As

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Generally: • no clouds, no aerosols : r = 0• clouds, no absorbing aerosols : r < 0• absorbing aerosols : r > 0

AAI: r > 0

Pros and Cons:+ AAI can detect UV absorbing aerosols:

volcanic ash, desert dust and smoke.+ AAI works in cloudy scenes.+ AAI works over ocean and land.

- AAI is an index: it depends on AOT (), SSA () and altitude ().- AAI is very sensitive to absolute calibration.

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Simulations of AAI for biomass burning aerosols

Clear-sky case Cloudy case

AAI increases with AOTAAI decreases with SZA

Nadir view

Aerosols at 4-5 km

Clouds at 1-2 km

DAK RTM simulationsWang et al., ACP, 2012

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Daily AAI map of GOME-2 spectral channels

http://www.temis.nl/airpollution/absaai/

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Daily AAI map from GOME-2 PMDs

http://www.temis.nl/o3msaf/vaac_pmd/

PMDs have 8x higher spatial resolution thanthe spectral channels

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Information for the VAAC (volcanic ash advisory centre)

http://www.temis.nl/o3msaf/vaac_pmd/

Eyjafjoll-eruptionof April-May 2010

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Smoke over Borneo from AAI, 1995 -2010

1997/1998 El Niño: drought caused many forest fires; 120.000 km2 forest burned.

Satellite data sources: GOME, SCIAMACHY, GOME-2

Figure: L.G. Tilstra, KNMI

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UV residue has two parts: Absorbing Index & Scattering Index

GOME-2 Aerosol Indices for July, 2011, cloud fraction < 0.2.

Work of Marloes Penning de Vries (MPIC, Mainz).Penning de Vries et al., ACP, 2012Penning de Vries, Visiting Scientist report of O3MSAF, 2012

Scattering aerosols and clouds Absorbing aerosols

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Effect of instrument degradation on the AAI

GOME-2

(for individual scan

mirror positions)

The global mean residue, the mean of all residues on a day between 60°N and

60°S, is about constant, showing only a very mild seasonal variation.

Instrument degradation has a very large impact on the residue/AAI:

2.3 % reflectance change ~ 1 AAI point.

Tilstra et al. (JGR, 2012) developed an in-flight degradation correction method.

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Aerosol Height retrieval

Approach: use cloud algorithm FRESCO for aerosol height

- FRESCO algorithm: fit of O2 A-band at 760 nm using a Lambertian reflector as cloud model.

- FRESCO v6 has two retrieval modes for 2 retrieved quantities:

Normal: Effective cloud fraction (cloud albedo 0.8) and Cloud height

Alternative: Scene albedo (cloud fraction 1) and Scene height

Wang et al., ACP, 2008

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FRESCO retrievals using simulated O2 A band spectra for dust aerosols

Clear-skyCloudy

Cloud layer

Aerosol layer

Wang et al., ACP, 2012

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Puyehue volcano (Chile), 20110606, Westerly Box

Wang et al., ACP, 2012

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Puyehue volcano (Chile), 20110606, Easterly Box

Wang et al., ACP, 2012

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Conclusions

• Absorbing aerosols, like desert dust, smoke, and volcanic ash can be detected by GOME-2

• GOME-2 provides near-real-time monitoring information on these aerosols, with the products:

- AAI for absorbing aerosols- SCI for scattering aerosols (if cloud mask is

used)- FRESCO for aerosol height.

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Links

• O3MSAF GOME-2 data products: http://o3msaf.fmi.fi

• TEMIS GOME-2 data products: http://www.temis.nl

• GOME-2 and Metop: http://www.eumetsat.int

• GOME-2 L0 data quality information: http://gome.eumetsat.int

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References on GOME(-2) aerosol retrievals M. de Graaf, P. Stammes, O. Torres, and R.B.A. Koelemeijer, Absorbing Aerosol Index: Sensitivity analysis,

application to GOME and comparison with TOMS, J. Geophys. Res. 110, D010201, doi:10.1029/2004JD005178, 2005.

M. de Graaf, L.G. Tilstra, P. Wang and P. Stammes, Retrieval of the aerosol direct radiative effect over clouds from space-borne spectrometry, J. Geophys. Res., 117, D07207, doi: 10.1029/2011JD017160, 2012

M. de Graaf and P. Stammes and E.A.A. Aben, Analysis of reflectance spectra of UV-absorbing aerosol scenes measured by SCIAMACHY, J. Geophys. Res. 112, D02206, doi: 10.1029/2006JD007249, 2007.

M. Penning de Vries, Beirle, S., and Wagner, T.: UV Aerosol Indices from SCIAMACHY: introducing the SCattering Index (SCI), Atmos. Chem. Phys., 9, 9555-9567, doi:10.5194/acp-9-9555-2009, 2009

M. Penning de Vries, and Wagner, T.: Modelled and measured effects of clouds on UV Aerosol Indices on a local, regional, and global scale, Atmos. Chem. Phys., 11, 12715-12735, doi:10.5194/acp-11-12715-2011, 2011.

L.G. Tilstra, M. de Graaf, I. Aben and P. Stammes, In-flight degradation correction of SCIAMACHY UV reflectances and Absorbing Aerosol Index, J. Geophys. Res., 117, D06209, doi: 10.1029/2011JD016957, 2012.

L.G. Tilstra, M. de Graaf, O.N.E. Tuinder, R.J. van der A, and P. Stammes, Studying trends in aerosol presence using the Absorbing Aerosol Index derived from GOME-1, SCIAMACHY, and GOME-2, Proceedings of the 2011 EUMETSAT Meteorological Satellite Conference, EUMETSAT P.59, ISBN 978-92-9110-093-4, 2011.

L.G. Tilstra, O.N.E. Tuinder, and P. Stammes, A new method for in-flight degradation correction of GOME-2 Earth reflectance measurements, with application to the Absorbing Aerosol Index, Proceedings of the 2012 EUMETSAT Meteorological Satellite Conference, EUMETSAT P.??, ISBN ??????????, 2012.

P. Wang, P. Stammes, R. van der A, G. Pinardi, M. van Roozendael, FRESCO+: an improved O2 A-band cloud retrieval algorithm for tropospheric trace gas retrievals, Atmospheric Chemistry and Physics, 8, 6565-6576, 2008

P. Wang, O.N.E. Tuinder, L.G. Tilstra, M. de Graaf, and P. Stammes, Interpretation of FRESCO cloud retrievals in

case of absorbing aerosol events, Atm. Chem. Phys., 12, doi: 10.5194/acp-12-9057-2012, 2012.

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Back-up slides

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Wavelength pair (nm)

Equator crossing time

Pixel size (km)

Days needed for global coverage

Platform / Operation period

GOME–1 340 / 380 10 : 30 LT 320 × 40 3ERS-2

(1995 – 2003*)

SCIAMACHY 340 / 380 10 : 00 LT 60 × 30 6Envisat

(2002 – 2012)

GOME–2 340 / 380 09 : 30 LT 80 × 40 1.5MetOp-A

(2006 – present)

OMI 354 / 388 13 : 30 LT 13 × 24 1Aura

(2004 – present)

AAI products from GOME, SCIAMACHY, GOME-2, and OMI

*GOME-1: loss of global coverage on 22 June 2003 ; instrument retired on 4 July 2011

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FRESCO retrievals using simulated O2 A band spectra for biomass burning aerosols

Clear-skyCloudy

Aerosol layer

Cloud layer

Wang et al., ACP, 2012

Australian WildfiresFeb 7th – Feb 12th 2009

Figure: O. Tuinder, KNMI