Land Surface Emissivity for MeghaTropiques MADRAS Channels

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Land Surface Emissivity for Megha-Tropiques
MADRAS Channels
Suresh Raju and K. Parameswaran Space Physics
Laboratory (SPL) Vikram Sarabhai Space Center,
(VSSC) Thiruvananthapuram 695 022
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• Objective
• Study the land surface emissivity at M-T window
  channels, 18, 23, 36, 89 and 157GHz on
  monthly/seasonal/annual average basis under clear
  sky condition.
• Improve the accuracy of lowest-layer water vapor
  sounding over land area
• Increase the use of M-T data for atmospheric
  studies over land area ??
• Estimate of land surface emissivities from
  satellite data is made and available in the form
  of Global Map (for example SSMI, AMSU channels -
  Prigent, Karbou, Eymard, Hewison, English, etc).

M-T Unlike other polar satellites, M-T has
random visit. Diurnal evolution of geophysical
parameters that affect land surface emissivity to
be investigated.
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• Limiatations
• Lack of established models
• for soil/vegetation dielectric-emissivity
  (Calvet et al. 1995)
• surface scattering model
• Limited Ground based/ airborne experiments to
  understand
• Angular, frequency and polarization dependence
• Soil humidity sampling layer (?/10), soil
  type? diurnal variation
• Skin temperature- diurnal variation (window),
  ? effective radiating temperature ?

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• Estimation of land surface emissivity (diurnal)
  from M-T MADRAS data under clear sky condition
• Approach
• Estimate atmospheric contribution to the
  satellite derived brightness temperature (Tb) by
  using the profiles of temperature and humidity of
  clear sky
• Subtract atmospheric contribution from the
  satellite measured Tb
• Estimate emissitvity using atmospheric corrected
  Tb and surface skin temperature derived from
  other sources (satellite data or insitu measured)
• Intercomparison with the collocated emissivity
  estimates (MAPS)

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Issues to be addressed Availability of accurate
skin temperature, humidity and temperature
profiles