Interactions: atmosphere

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Interactionsatmosphere

• EG2234
• Earth Observation

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Topics

• Historical Overview
• Demands and Characteristics
• Routine analysis (weather/climate work)
• Cloud Motion Vectors
• METEOSAT
• References

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Historical Overview

• Atmospheric RS has mostly been performed with
  geostationary satellites
• In 1960s NASA developed the ATS-1 with a cloud
  camera
• Later ATS-3 was equipped with a colour cloud
  camera but no real multispectral capabilities

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ATS-1
Source NASA/GSFC, 2008
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Historical Overview

• First truly geosynchronous SMS (Synchronous
  Meteorological Satellite) was launched in 1974
• First real multispectral satellite launched in
  mid 1970s was the Geostationary Operational
  Environmental Satellite (GOES) launched in the
  late 1970s

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Source NASA/GSFC, 2008
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Demands Characteristics

• A geostationary orbit requires the satellite to
  move at the same rate as the Earth
• The orbit of the satellite must follow the
  equatorial plane of Earth
• Changes to satellite orbit uses hydrazine
  propulsion system
• Ground to satellite telemetry allows orbital
  adjustment instructions to be sent

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Geosynchronous orbital parameters By
season Adapted from Chen, 2001
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Demands Characteristics

• The type of data required is determined by
  altitude of target phenomena
• Some satellites are better equipped to analyse
  specific types of phenomena
• Key requirements are those that deal with
  atmospheric threats (e.g. hurricanes) or
  atmospheric column water vapour content for cloud
  seeding

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Adapted from Chen, 2001
atmosphere
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Demands Characteristics

• In order to escape Earths gravitational field
  geostationary satellites MUST be at least
  35,800km from surface
• Due to synchronous orbit, images can be updated
  every 15 minutes
• Due to long distance from Earth, images are of a
  poorer spatial resolution (less detail) than
  polar orbiting satellites

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Routine Analysis

• Use of visible images to determine positions of
  cloud formations and storm systems (based on
  albedo)
• Use of thermal infrared images to determine cloud
  temperatures and probability of rainfall
• Use of water vapour images to ascertain
  tropospheric water vapour content

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Cloud Motion Vectors

• CMVs allow windspeed to be determined
• Usually, IR-WV images are used to track a
  specific cloud formation
• Sequence of images allows cloud formation to be
  tracked so that speed and direction can be
  calculated
• Final map shows streamlines over a region

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Step 1 Isolate a cloud formation
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Step 2 New position in 60 mins gives speed and
direction
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e.g 22 degrees and 35 metres per second
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Allows us to create a streamline
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METEOSAT

• Primary European weather satellite
• Meteosat-1 first launched in 1977
• Latest version is MSG (Meteosat Second
  Generation)
• Controlled by Eumetsat (originally by the
  European Space Agency)
• High degree of continuity since 1977 to 2007

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Eumetsat HQ in Darmstadt, Germany
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Overview of Meteosat system
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Classic Meteosat Satellite VISIBLE
0.5-0.9µm IR-WV 5.7-7.1µm IR-THERMAL
10.5-12.5µm
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Primary ground segment antennas in Fucino
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Mission Control Pre-processing
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Main system data flows
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2D Image Histogram
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Histogram Interpretation
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Automated cloud motion vector winds
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Cloud analysis
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Eumetsat Post-processing For meteorological Analys
is
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Dissemination of products
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Global coverage of geostationary satellite systems
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References

• The Meteosat System (1996), Published by
  Eumetsat. Pub Ref EUM TD 05
• Geostationary weather remote sensing systems
  (2001) By Chen H.S. Published by Xlibris, US.
• Eumetsat website
• http//www.eumetsat.de