Variability of Worldwide Cloud Cover

Understanding how droughts form and how to predict them have been of increasing concern. Cloud data for the whole world based on satellite imagery are available from the ISCCP for the time period of 1983-2008. By utilizing the D2 data sets from the ISCCP, we looked at patterns in cloudiness over the world. The goal is to relate the patterns found to those in other measures of drought such as evaporation and precipitation with the purpose of better understanding how droughts take place and improving drought prediction. In the current research, we mapped correlation timescales for yearly-mean cloudiness over the observation period, as well as the correlation length scale of yearly cloudiness. We found higher correlations in the mid-latitudes and in less cloudy areas. We hypothesize that changes in such correlation patterns might serve as an indicator of developing drought.