Here are a collection of plots (see tar file link at left) showing time series of surface observed total cloud and ISCCP total cloud globally averaged over land only, ocean only, and land+ocean during the time period that the datasets overlap. I also show the spatial pattern of correlation of each local grid box time series with the global time series. It seems that there is more agreement between ISCCP and surface-observed cloudiness over land than over ocean, something that I have previously found.

The surface-observed land total cloud time series exhibits no trend, unlike the case for the ISCCP land total cloud time series, which exhibits a maximum in the late 1980s and a minimum in the mid 1990s. Most land grid boxes have a positive correlation with the surface land total cloud time series, especially Africa and southwest Asia. Anticorrelations with the global time series occur in southeast Asia.

The surface-observed ocean total cloud time series exhibits an upward trend, in contrast to the downward trend in the ISCCP ocean total cloud time series. Most ocean grid boxes have a small positive correlation with the surface ocean total cloud time series.

Given the larger area of the ocean, the land+ocean time series resemble the ocean time series. The ISCCP land+ocean correlation plot also exhibits satellite artifacts, and the surface observed land+ocean plot shows no physically intuitive pattern, and positive correlations predominate.