Status of the mission and preliminary definition

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• Status of the mission and preliminary definition
• of rain retrieval algorithms

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MEGHA-TROPIQUES

• ISRO CNES mission aimed to study water cycle and
  energy exchanges in tropical zone
• Main objectives
• Energy budget of the atmosphere (radiation and
  latent heat) at scales from the whole
  intertropical zone the scale of convective
  systems
• Life cycle of tropical convective systems and
  associated water budgets
• Relationships and feedbacks between convection,
  water vapour and radiation

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Principles of the mission Megha-Tropiques

• Measure simultaneously 3 parameters determining
  for the energy budgets of the atmosphere
• radiative fluxes (ScaRaB),
• water vapour distribution (Saphir)
• precipitation (Madras)
• Accounting for the variability of the phenomena
  and th large range of scales, repetitivity of
  measurement is privileged relative to the ground
  resolution high orbit (870 km), low
  equatorial inclination (20), resolution 10 to 40
  km.

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The Instruments

• ScaRaB a wide band radiometer for radiative
  fluxes measurement (transversal scan, 40 km)
• Saphir a microwave water vapour sounder. 6
  channels around 183.31 GHz. (transversal scan, 10
  km)
• Madras a microwave imager
• 5 channels 18, 23, 37, 89 and 157 GHz
• (conical scan,
• Marfeq is the radiofrequency part of this
  instrument

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Project status (in France)

• SCARAB already flown instrument Phase B1
  ended Nov 2003
• SAPHIR New development Phase B1 ended Nov
  2003
• MARFEQ Astrium company
• New development - Phase B ended in october 2003

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2004 new start thanks tonew sharing with ISRO

• ISRO accepts to shift from the PROTEUS platform
  to an Indian platform, and to take the
  corresponding responsibilities (system, ground
  control,)
• CNES is keeping the responsibility of the ScaRaB
  and SAPHIR instruments, and MARFEQ, the
  radiofrequency part of MADRAS

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Preliminary new planning

• New start june 2004
• Complementary phase B studies with ISRO (platform
  change)
• Minimal MARFEQ activity in 2004
• Start of complementary phase B studies for
  SAPHIR/SCARAB
• Start of phase C/D MARFEQ January 2005
• Delivery of MARFEQ end 2007
• Delivery SAPHIR/SCARAB end 2007
• launch 2009

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Status of rain retrieval algorithms (France)

• Two kind of studies
• passive microwave algorithm (N. Viltard et al.)
• (BRAIN)
• combined leo-geo algorithm (M. Desbois et al.)
• Re-scaling algorithm

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Algorithm General Principle
Database Construction
Brightness Temperatures
Atmos. Variables
DataBase
Co-located (TMIPR) or
Cloud Model SimulationRTM
or Hybrid of the two
Retrieval Algorithm
Measured brightness Temperatures
Algorithm
Bayesian or Neuronal
Retrieved Variable
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BRAIN Algorithm Principle

• Derived from Gprof
• Bayesian approach
• Co-located data of TMI and PR
• Completion with model simulation
• Test base for error estimation

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BRAIN Performances for TMI
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BRAIN for MADRAS Algorithm

• PR profile used to find a matching cloud model
  simulation profile in a primary database
• Use a RTM to simulate TBs for MADRAS and TMI

• Use TMI channels simulated vs. observed to infer
  error (also for Madras)
• Build Madras database for BRAIN algorithm

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Combined GEO-IR microwave (re-scaling algorithm)
Tests over Africa PR used as rainfall detector
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Rainfall probability of occurencefrom Meteosat/PR
Systems rainfall efficiency deduced from
comparisons with Monthly GPCP
July 2000 tests and validation data
Monthly results in terms of monthly rainfall
Available validation data (collected by IRD)
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Statistical indicators show some improvements
relative to a product as GPCP. This is still more
valid at smaller time scales (10 days).
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Further developments

• use of new channels of MSG to improve the rain
  detection part of the re-scaling algorithm
• Validation of BRAIN over Africa
• Chaining between BRAIN and the re-scaling
  algorithm
• Further validation studies over Africa during the
  AMMA experiment (African Monsoon Multiscale
  Experiment)
• Hoping very much to have TRMM working during the
  most intensive phases of AMMA (2005-2007)