Satellitederived Sea Surface Temperatures

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Satellite-derived Sea Surface Temperatures

• Corey Farley
• Remote Sensing
• May 8, 2002

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Satellites

• GOES Imager
• Continuous coverage
• High temporal resolution
• Polar Imager
• Advanced Very High Resolution Radiometer
• Global coverage
• Better data resolution that GOES
• Do not provide continuous coverage

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GOES Imager
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Polar ImagerAdvanced Very High Resolution
Radiometer
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Technique for estimating SST

• An algorithm was created using channel 4 (10.7
  micron) and channel 5 (12.0 micron) of the GOES
  and Polar satellites.
• Radiance values are obtained for both channels
  and brightness temperatures are calculated.
• SSTs can be calculated using brightness
  temperatures and regression coefficients.

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Weighting Functions
Referred to as the split window channels The
12.0 micron window is more sensitive to moisture
than the 10.7 micron and most of the
radiance comes from the earths surface. The 10.7
detects surface radiation and also radiation from
low clouds.
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Limitations of using radiance measurements

• Clouds block infrared radiation, causing
  errors in brightness temperature values.
• The atmosphere absorbs some radiation emitted by
  the surface and emits radiation back to the
  surface and to the satellite.
• Some solar radiation is reflected from the
  surface to the satellite.
• Some of these effects are wavelength dependent
  and can corrected by using multiple wavelengths.

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SST EquationsGOES Imager

• GOES-8/9 SST -6.4110 1.0260 T4 1.1900 (T4
  T5) 0.2017 (T4 - T5)2
• GOES-10 SST 18.3500 0.9459 T4 0.4261 (T4 -
  T5) 0.4473 (T4 - T5)2
• Screening for cloud contamination and other
  factors were performed to ensure clear air
  radiance values.
• The coefficients are empirically determined by
  comparing satellite and buoy measurements.
• Accuracy Standard deviation varied from 0.6 to
  0.8 K. Calculated by comparing GOES Imager and
  buoy data.

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SST EquationsPolar Imager AVHRR
Theta is the sensor zenith angle T- the
brightness temperatures at different
wavelengths A- empirically derived coefficients
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Applications

• Since SST values can be obtained frequently, we
  can monitor different phenomena.
• Track El Nino and La Nina
• Ocean currents such as the Gulf Stream can be
  tracked.

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Hurricane Eduardo Track
Upwelling by Eduardo caused cooler water at the
sea surface.
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Ocean Currents
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QUESTIONS???