Inter-calibration of the SEVIRI VIS0.6 channel with MODIS Aqua, using Deep Convective Clouds as transfer targets S

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Inter-calibration of the SEVIRI VIS0.6 channel
with MODIS Aqua, using Deep Convective Clouds as
transfer targetsSébastien Wagner, Tim Hewison

• CONTEXT
• Past and current geostationary imagers no
  on-board calibration for the Solar Reflective
  Bands.
• ? Calibration exclusively based on vicarious
  approaches using various target types (e.g.
  deserts, clouds, oceans, Moon).
• Constellation of geostationary satellites do not
  see the same targets (in particular deserts and
  oceans)
• ? Data sets harmonization and comparability are
  challenging.
• SCOPE
• Comparability achievable through the use of a
  common reference instrument on-board a polar
  satellite
• Which reference for Solar Reflective Bands? GSICS
  recommendation MODIS/Aqua
• Which targets? In order to reduce uncertainties ?
  inter-calibration over similar targets with well
  characterized radiative properties such as Deep
  Convective Clouds
• Which method? Implementation of the algorithm
  developed by Doelling et al. (2011), applied to
  the VIS0.6 channel, available on the Spinning
  Enhanced Visible and Infrared Imager (SEVIRI)
  aboard the Meteosat-8, - 9 and -10 satellites
  with MODIS-Aqua.

PROVIDING CORRECTIONS TO ENSURE COMPARIBILITY AND
HOMOGENEITY
GOS Global observing System RSB Reflective
solar bands
GOS Level 1 b/c producers, in charge of the data absolute calibration
GSICS Corrections (inter-calibration, tie to common reference(s)). For Reflective Solar Bands, current activities include inter-calibration with MODIS using
Users Provide feedback on data usage, data quality and accuracy
Example of DCCs tracking with MODIS and SEVIRI as
implemented
Preliminary results for a few cases... as shown
in September 2012
Possible reasons for bad results and solutions...

• Standard uncertainty u / mean lt 0.2 with
• Sampling problem but not only...
• MODIS PDF derived dynamically (in parallel with
  SEVIRI PDF) ? wrong!
• MODIS PDF to be derived for a time interval in
  early years of operations
• Implementation of the ADM correction
• Angle calculation
• Correction calculation
• Other reasons?

NEW RESULTS AFTER LATEST DEVELOPMENTS... STILL
NOT SATISFYING!
COMPARISONS OF THE PDFS BEFORE AND AFTER ADM
CORRECTIONS
Govaerts, Y. M. and M. Clerici (2004).
"Evaluation of radiative transfer simulations
over bright desert calibration sites." IEEE TGRS
42(1) 176-187. Govaerts, Y. M., M. Clerici,
Clerbaux N. (2004). "Operational Calibration of
the Meteosat Radiometer VIS Band." IEEE TGRS
42(9) 1900-1914. Govaerts, Y. M., and Clerici,
M. (2004). MSG-1/SEVIRI Solar Channels
Calibration Commissioning Activity Report
(EUMETSAT). Doelling D. et al. (2011), ATBD
for Deep Convective Cloud technique of
calibrating GEO sensors with Aqua-MODIS for
GSICS, https//gsics.nesdis.noaa.gov/pub/Developm
ent/AtbdCentral/GSICS_ATBD_DCC_NASA_2011_09.pdf.