The Saharan Air Layer and the Fate of African Easterly Waves—NASA's AMMA Field Study of Tropical Cyclogenesis

• DOI: 10.1175/2009bams2728.1
• Publication Date: 2009-04-01T19:49:46Z
• Authors: Edward J. Zipser; Cynthia H. Twohy; Si-Chee Tsay; K. Lee Thornhill; Simone Tanelli; Robert Ross; T. N. Krishnamurti; Q. Ji; Gregory Jenkins; Syed Ismail; N. Christina Hsu; Robbie Hood; Gerald M. Heymsfield; Andrew Heymsfield; Jeffrey Halverson; H. Michael Goodman; Richard Ferrare; Jason P. Dunion; Michael Douglas; Robert Cifelli; Gao Chen; Edward V. Browell; Bruce Anderson
• Keywords: African easterly jet; Tropical cyclogenesis; Cape verde; Cyclogenesis; Dropsonde; Tropical Atlantic

In 2006, NASA led a field campaign to investigate the factors that control fate of African easterly waves (AEWs) moving westward into tropical Atlantic Ocean. Aircraft and surface-based equipment were based on Cape Verde's islands, helping fill some data void between Africa Caribbean. Taking advantage international Monsoon Multidisciplinary Analysis (AMMA) program over continent, NASA-AMMA (NAMMA) used enhanced upstream data, whereas NOAA aircraft farther west in studied several storms downstream. Seven AEWs during AMMA, with at least two becoming cyclones. Some did not develop while being sampled near Verde likely intensified central instead. NAMMA observations able distinguish large-scale wave structure smaller-scale vorticity maxima often form within waves. A special complication east environment is Saharan air layer (SAL), which frequently accompanies may introduce dry heavy aerosol loading convective storm systems AEWs. One main achievements was acquisition database remote sensing situ properties SAL, enabling dynamic models satellite retrieval algorithms be evaluated against high-quality real data. Ongoing research this will help determine how SAL influences cloud microphysics perhaps also cyclogenesis, as well more general question recognizing small-scale are become