Climate-scale Variations in Stratocumulus Cloud Amount

Observational evidence indicates that monthly/seasonally averaged stratocumulus cloud amount is strongly correlated with lower tropospheric static stability, defined as the difference between the potential temperature at 700 millibars and the sea surface temperature. This correlation appears to hold for seasonal, interregional, and interannual variations in cloud amount. A linear analysis shows that stratocumulus cloud amount increases 6% for every degree Celsius increase in static stability.

We will briefly review the global stratocumulus cloud climatology emphasizing a) the seasonal cycle of stratocumulus and how it is correlated with the seasonal cycle of the static stability and b) the extensive amount of (not widely recognized) summertime stratus/fog found over the midlatitude oceans. Subsequently we will present theories explaining the correlation between monthly averaged static stability and monthly averaged stratocumulus cloud amount.