MODIS Spectral Test.

0.86 reflectance (x-axis) versus the percentage of pixels less then that value (e.g. cloud fraction if this reflectance was a threshold ) for ocean scenes solar zenith angles and viewing angle s between 0 - 10 degrees and 30 - 40 degrees. For different viewing geometries, the cloud detection threshold varies.

At low reflectances (less then 10 %) a small change in the threshold can result in a large change in cloud amount.

A sensitivity analysis of the MODIS cloud mask to threholds variations similar to calibration issues.