@article{tomkins_mechem_yuter_rhodes_2021, title={Regional Flow Conditions Associated with Stratocumulus Cloud-Eroding Boundaries over the Southeast Atlantice}, volume={149}, ISSN={["1520-0493"]}, DOI={10.1175/MWR-D-20-0250.1}, abstractNote={Large, abrupt clearing events have been documented in the marine stratocumulus cloud deck over the subtropical Southeast Atlantic Ocean. In these events, clouds are rapidly eroded along a line hundreds–to–thousands of kilometers in length that generally moves westward away from the coast. Because marine stratocumulus clouds exert a strong cooling effect on the planet, any phenomenon that acts to erode large areas of low clouds may be climatically important. Previous satellite-based research suggests that the cloud-eroding boundaries may be caused by westward-propagating atmospheric gravity waves rather than simple advection of the cloud. The behavior of the coastal offshore flow, which is proposed as a fundamental physical mechanism associated with the clearing events, is explored using the Weather Research and Forecasting model. Results are presented from several week-long simulations in the month of May when cloud-eroding boundaries exhibit maximum frequency. Two simulations cover periods containing multiple cloud-eroding boundaries (active periods), and two other simulations cover periods without any cloud-eroding boundaries (null periods). Passive tracers and an analysis of mass flux are used to assess the character of the diurnal west-African coastal circulation. Results indicate that the active periods containing cloud-eroding boundaries regularly experience stronger and deeper nocturnal offshore flow from the continent above the marine boundary layer, compared to the null periods. Additionally, we find that the boundary layer height is higher in the null periods than in the active periods, suggesting that the active periods are associated with areas of thinner clouds that may be more susceptible to cloud erosion.}, number={6}, journal={MONTHLY WEATHER REVIEW}, author={Tomkins, Laura M. and Mechem, David B. and Yuter, Sandra E. and Rhodes, Spencer R.}, year={2021}, month={Jun}, pages={1903–1917} }
 @article{yuter_hader_miller_mechem_2018, title={Abrupt cloud clearing of marine stratocumulus in the subtropical southeast Atlantic}, volume={361}, ISSN={["1095-9203"]}, DOI={10.1126/science.aar5836}, abstractNote={A shrinking marine refrigerator Low subtropical marine clouds scatter solar radiation back to space and thereby cool the climate system. Most work on understanding changes in the coverage of these types of clouds has focused on the effects of sea surface temperatures or on aerosols. Yuter et al. show that dynamic effects due to atmospheric gravity waves are responsible for the rapid clearing of large areas of these clouds. This phenomenon also has implications for marine ecology and biogeochemistry. Science, this issue p. 697 Atmospheric gravity waves can rapidly erode subtropical marine low cloud fronts. We document rapid and abrupt clearings of large portions of the subtropical marine low cloud deck that have implications for the global radiation balance and climate sensitivity. Over the southeast Atlantic, large areas of stratocumulus are quickly eroded, yielding partial or complete clearing along sharp transitions hundreds to thousands of kilometers in length that move westward at 8 to 12 meters per second and travel as far as 1000+ kilometers from the African coast. The westward-moving cloudiness reductions have an annual peak in occurrence in the period from April through June. The cloud erosion boundaries reduce cloud at ≈10-kilometer scale in less than 15 minutes, move approximately perpendicular to the mean flow, and are often accompanied by small-scale wave features. Observations suggest that the cloud erosion is caused by atmospheric gravity waves.}, number={6403}, journal={SCIENCE}, publisher={American Association for the Advancement of Science (AAAS)}, author={Yuter, Sandra E. and Hader, John D. and Miller, Matthew A. and Mechem, David B.}, year={2018}, month={Aug}, pages={697-+} }