GLSEA

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GLSEA - Great Lakes Surface Environmental
Analysis (Schwab, Leshkevich and Muhr, 1999, JGLR
25(3))

• GLSEA Great Lakes Surface Environmental
  Analysis
• Based on NOAA CoastWatch AVHRR SST imagery
• Great Lakes synoptic window, 512x512 2.6 km
  pixels
• Linear geocorrection
• 7 daytime, 5 nighttime cloud masks
• Composite and (3x3) smooth
• 5-day average
• Produced daily at GLERL since 1994

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• Algorithm for GLSEA
• For each day
• 1. Get GLSEA from previous day
• 2. Get all SST images from last 24 hours
• 3. Geocorrect SST images and apply cloud mask
• 4. For each lake, overlay latest SST data if
  areal coverage gt 5
• 5. If areal coverage for lake is gt 20, then
  adjust rest of lake by difference from previous
  day (in valid area)
• 6. Smooth with 9 point average
• 7. Average last 5 days and save GLSEA
• 8. Overlay latest NIC ice chart

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Algorithm for GLSEA2 For each day 1. Get
GLSEA from previous day 2. Get all SST images
from /- 10 days (20 day window) 3. Geocorrect
SST images and apply cloud mask 4. For each
cell in GLSEA 4.1 Get all SST values for this
cell from /- 10 days (20 day window) 4.2 If
there are more than 2 values in /- 10 day
window, calculate mean and standard
deviation, eliminate values more than 2 standard
deviations away from mean 4.3 If there are
both a prior SST value and a subsequent SST value
for this cell within /- 10 day window,
then linearly interpolate in time,
else if there is at least one SST value for
this cell within /- 2 days, use it 5. For any
pixel not filled in Step 4 5.1 If there are
at least 6 SST values that have been filled in
Step 4 in the surrounding 5x5 cells, use
the average of the surrounding cells for this
cell, else fill this cell with value
of cell from previous day plus change in lakewide
mean 6. Calculate lakewide mean for each lake
and save GLSEA
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GLSEA
GLSEA2
0.92
1.04
0.70
0.81
1.49
0.89
1.00
0.79
1.58
1.38
1.10
1.03
1.41
1.12
1.45
1.01
Comparison with NDBC buoy daily average SWT
1995-97
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GLSEA2 - New Great Lakes Surface Environmental
Analysis

• Based on NOAA CoastWatch AVHRR SST imagery
• Great Lakes synoptic window, 512x512 2.6 km
  pixels (1995-2003)
• 1024x1024 (2004)
• Linear geocorrection
• 7 daytime, 5 nighttime cloud masks
• Cell-based interpolation/extrapolation procedure
• No artificial smoothing