ESA-JAXA Pre-Launch EarthCARE
Science and Validation Workshop
13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy

Assessment of the effect EarthCARE Multi-spectral imager spectral
misalignment for aerosol and cloud property retrievals
Anja Hünerbein 1, Nicole Docter 2, and René Preusker 2(1) Leibniz Institute for Tropospheric Research, Leipzig, Germany(2) Free University Berlin

Content▪ Introduction MSI spectral misalignment▪ Spectral forward simulation:▪ Gas transmission▪ Surface description▪ Aerosol and cloud properties▪ Error quantification on the MSI L2 aerosol and cloud product▪ MSI smile scene

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Introduction MSI spectral misalignment
Multi-Spectral Imager (MSI):
Channel
VIS
NIR
SWIR-1
SWIR-2
TIR 1
TIR 2
TIR 3

Center Wavelength
m
0.67
0.865
1.65
2.21
8.80
10.80
12.00

SWIR-2 radiator

Bandwidth
(50%)
20 nm
20 nm
50 nm
0.1 m0.9 m0.9 m0.9 mTIRVNSOBSun Baffle

Determination of cloud and aerosol properties and horizontal structures of clouds
 baseline-products comparable to MODIS products (follow-on A-Train)▪ cloud cover and cloud phase▪ cloud optical and physical properties▪ aerosol properties
 synergy with active instruments
ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Introduction MSI spectral misalignment
NIR
VIS

SWIR1
SWIR2

• Central wavelength are calculated from the filter function

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Introduction MSI spectral misalignmentNIRVIS

14 nm

SWIR120 nm

▪

SWIR2

Spectral forward simulation based on radiative transfer model :▪ Gas transmission▪ Surface description▪ Aerosol and cloud properties

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

MSI smile effect on gaseous absorption➔ Transmission based on CKDMIP (Hogan and Matricardi, 2020)

VISNIR

SWIR1

SWIR2

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

MSI smile effect on gaseous absorption
Relative error on normalized TOA radiance:

VIS

absorption of ozone and water vapour
relative error 3.3%

NIR

SWIR1

SWIR2

absorption of methane and carbon dioxide
relative error -0.1 to 0.3%

relative error below +/-0.5%

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

MSI smile effect on surface description
Based on Bowker et al. 1985 (grass, wheat, birch) and ECOSTRESS spectral library version 1.0 (snow)
NIR

VIS
red edge

SWIR1

SWIR2

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.de

contact:

MSI smile effect on surface description
Relative error on normalized TOA radiancerelative error up to 50% (grass)

VIS

NIR

SWIR1

SWIR2

relative error varies between-7.3% and 16.3% (snow), -2.1% and 4.5% (grass)

relative error is about
1% (grass) and up 5.3% (snow)

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.de

contact:Impact aerosol and cloud properties
Example is given for:• Different aerosol types for AOT 0.3• Liquid cloud with reff = 5µm and ice cloud with reff = 10µm
and COT 10VIS
NIR

SWIR1

SWIR2

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:Impact aerosol and cloud properties
Relative error on normalized TOA radiance over grass
Up to 27% for coarse mode and 30% for finemode, ice clouds up to 2%VIS

NIR

SWIR1

SWIR2-1.9%- 4.2% for coarse mode and -2%- 4.4% for fine mode,
ice clouds 1.4%- -0,8%
ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Error quantification for MSI L2 product
Synthetic MSI smile block scene with the EarthCARE simulator (Donovan et al. 2023)

Two ECSIM runs:

1. Ideal condition
2. Contains the SMILE affected quantities as surface, gas, aerosol and cloud properties

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Error quantification for MSI L2 productThe differences between the two runs are shown as relative error of thenormalized TOA radiances.
VIS

NIR

SWIR1

SWIR2

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Error quantification for MSI L2 productThe differences between the two runs are shown as relative error of thenormalized TOA radiances.
Over forest -2% for aerosol, absorption due to gas over all underestimation
Over barren up to 1.3% surface type dominate

VISNIR

SWIR1

SWIR2Cirrus: 1.3% forest, barren surface cloud (single scattering albedo place a role)
ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Error quantification for MSI L2 product
Over landOver ocean• AOT at 670nm is highest -48% fine mode strong absorbing• AOT at 670nm over land underestimated up to -30% fine mode less absorbing• Error decrease for higher AOT loading and bigger particles (dust)

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Error quantification for MSI L2 product
Over land

COTREFF• Cloud dominated by the surface properties for optical thin clouds stratocumulus still
up to -3 %• Cloud effective radius with small effective radius is smaller but with higher cloud
effective radius error from 7.5% up to -5%

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact:

Conclusion
MSI spectral misalignment:• MSI shows a cross track central wavelength variation in VIS and SWIR channel of up to 14 and 20 nm• For low optical thickness of aerosol and cloud (less than 8) we found significant error caused by gas
absorption, surfaces as well as cloud properties• Measured Level 1 signal is not planned to be corrected,
but the Level 2 retrieval M-AOT (Docter et al. 2023) and M-CLD (Hünerbein et al. 2023) will adapt thelook up tables: for gas correction coefficients, surface parameterization coefficients, aerosol and cloudsee more -> Docter et al, 2023 in the special issue of EarthCARE in AMT• Thanks to the RTTOV team the TIR coefficients are calculated and available now

ESA-JAXA Pre-Launch EarthCARE Science and Validation Workshop | 13 – 17 November 2023 | ESA-ESRIN, Frascati (Rome), Italy
anjah@tropos.decontact: