Series of AVHRR channel 1 observations over a grassland site in Inner Mongolia PRC showing the effects of contamination by clouds and cloud-cast shadows (note that the lowest value is from a shadowed AM observation).
For the processing chain developed for this study, the screening was carried out in two stages : 1) calculation of the mean_1 and population standard deviation_1 from the entire sequence of observations and then 2) recalculation of a new mean_2 and population standard deviation_2 using only those observations within the mean_1 plus or minus 0.8stddev_1 (shown above). Thresholds for cloud and cloud shadow were then set at : mean_2+(1.9*stddev_2) for the upper (cloud) limit and mean_2-(1.4*stddev_2) for the lower (cloudshadow) limit (not shown).