The Effects Of Snow Cover on Surface Albedo

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The Effects Of Snow Cover on Surface Albedo

• Darren Hardy
• ESM 266 (Dozier)
• Spring 2005

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Global Warming

• Earth Observing System measurement objectives
• Global warming
• Long-term climate change
• Socio-economic implications
• Research questions
• Climate system response to human forcing
• Land cover and socio-economic interactions

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(IPCC, 2001)
(Asrar Dozier, 1994)
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Surface Albedo

• Surface albedo
• Reflectivity at the Earths surface
• King et al. (1997, p. 160)
• Lack good global data on albedo over land
• Albedo data products
• ASTER AST13
• CERES ES-9
• MISR MIS04, MIS05
• MODIS MOD09, MOD43

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Snow Cover

• Critical component of global energy budget
• High albedo Low absorption
• Snow reflects radiation back to space
• Global mean snow albedo contributes to warming of
  the atmosphere
• Mean snow cover ?, Mean surface albedo ?

(King et al., 1997, p. 196) (Stroeve et al.,
2005, p. 46)
snowflakebentley.com
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Question

• How does observed snow cover correlate with
  observed surface albedo?
• Theory linear correlation
• Data Products
• MOD09A1 (surface reflectance, 8-day)
• MOD10A1 (snow cover, daily)
• MOD10A2 (snow cover, 8-day)

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MOD09A1

• MODIS/Terra Surface Reflectance 8-Day L3 Global
  500m SIN Grid
• 7 Bands (centered 648, 858, 470, 555, 1240,
  1640, 2130 nm)
• From MODIS Level 1B
• Zeniths, azimuth
• Quality control

RGB (Band 1, Band 4, Band 3) April 7, 2001
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MOD10A1

• MODIS/Terra Snow Cover Daily L3 Global 500m SIN
  Grid V004
• algorithm (Snowmap)
• Normalized Difference Snow Index (NDSI)

Grayscale (Snow Cover) April 7, 2001
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MOD10A2

• MODIS/Terra Snow Cover 8-Day L3 Global 500m SIN
  Grid
• same as A1
• Snowmap
• Composite of 8 days

Grayscale (8-day Snow Cover) April 7, 2001
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MOD09A1Surface Albedo
RGB (Band 1, Band 4, Band 3) April 7, 2001
RGB (Band 5, Band 6, Band 7) April 7, 2001
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MOD10A2Snow Cover
Grayscale (8-day Snow Cover) April 7, 2001
Grayscale (Maximum Snow Extent) April 7, 2001
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Analysis Preparation

• Research MODIS data products
• Search for MOD09A1, MOD10A1/2
• Study Area is California
• EOS Data Gateway
• Download granules (2001089, 2001097)
• Land Processes DAAC
• National Snow and Ice Data Center DAAC
• Define Region of Interest for California

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Analysis Overview

• Projection
• Mercator (WGS84)
• Georeferenced
• Link geographic
• Correlate albedo with snow cover
• MOD09A1 (8-day)
• surface albedo
• Bands 1 7
• MOD10A2 (8-day)
• snow cover (max ext)

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Step 1Compute total surface albedo
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Step 2Filter 8-day Snow Cover
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Step 3Compare Albedo Snow Cover
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2
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Results
April 7, 2001
White is 100 correlation Black is no snow
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Results
Lake Tahoe
April 7, 2001
White is 100 correlation Black is no snow
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Histogram of Results
snow cover vs. surface albedo differences
large difference small difference
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Temporal ComparisonTotal Surface Albedo
April 7, 2001
April 7, 2000
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Temporal ComparisonSnow Cover
April 7, 2001
April 7, 2000
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Temporal ComparisonResults
April 7, 2001
April 7, 2000
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Temporal ComparisonResults
April 7, 2001
April 7, 2000
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Greenland EarthAsArt.gsfc.nasa.gov