Comparison MODIS Cloud Mask with ARCL - ARM SGP:

Comparison of MODIS cloud mask and ARCL over the SGP site for the years 2003, 2004 and 2005, daylight hours (Terra - Aqua in paranthesis). MODIS 5 by 5 pixels around the SGP are averaged to get MODIS cloud amount and then compared to ARCL cloud fraction over a 30 minute time perioud, were ARCL cloud fraction of less than 5% is considered clear. MODIS confidences of greater than 0.95 are considered clear.

Agreement between the two approaches is 84% agreement for Terra, 82% for Aqua.

  ARCL Clear  ARCL Cloud 
MODIS Clear  146 (117)   45 (58)  
MODIS Cloudy   38 (12)  298 (185)  

The ARCL cloud amount at different resolutions, comparisons are for 10 minute averages:

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Some of the points that are classified differently between MODIS and ARCL:

 

Finally, here is a comparison of monthly mean cloud fraction from MODIS over the ARM site with the ground based observations provided by Jay Mace.

MODS vs ARM SGP