Motion Characteristics of Propagating Cloud-Eroding Boundaries in the Subtropical Southeast Atlantic

Clouds play an important role in the radiative balance of the Earth and can both warm and cool the air depending on the cloud top height and underlying surface characteristics. Large decks of marine stratocumulus commonly form in the subtropical southeast Atlantic off the coasts of Angola and Namibia, and often extend thousands of km to the east. Recent work has shown that vast areas of these marine low clouds can be eroded along westward-moving sharp lines the length of California. The cloud-eroding boundaries can reduce cloud at ~10 km scale in less than 15 minutes and can travel up to 1000+ km from the African coast. The propagation speed of the line is a key characteristic used to rule in or rule out candidate mechanisms for cloud erosion. Previous work generated a climatology of the occurrences of these boundaries through detailed analysis of 10 years of NASA EOSDIS Worldview satellite imagery. In this project, we utilize sequences of IR satellite images to generate Hovmöller diagrams which are in turn used to estimate the speed of the cloud-eroding boundaries relative to increasing distance from the coast. The eventual goal of this project is to determine the distribution of motion characteristics for the several hundred boundaries in the climatology.