Two types of ridging South Atlantic Ocean anticyclones over South Africa and the associated dynamical processes

Show simple item record Ndarana, Thando Rammopo, Tsholanang S. Reason, Chris J.C. Bopape, Mary-Jane Morongwa Engelbrecht, Francois A. Chikoore, Hector 2021-11-29T14:46:54Z 2021-11-29T14:46:54Z 2022-01
dc.description.abstract Using 41 years of ERA5 reanalysis, two types of ridging South Atlantic Ocean high pressure systems were identified in the South African domain. Type-N events have a zonal structure and the ridging component breaks off from the parent South Atlantic Ocean anticyclone, after extending across the South African mainland. Type-S events extend south of the mainland and then break off. The Type-N (Type-S) ridging component is weaker (stronger) leaving behind a stronger (weaker) South Atlantic Ocean high. The two types of ridging events are associated with different configurations of Rossby wave packets that propagate across the South Atlantic Ocean. Surface and upper tropospheric anomalies associated with Type-S wave packets are stronger than those associated with Type-N events and the vertical coupling of the anomalies is much stronger during Type-S events. Type-N events are associated with a double jet streak structure, with the downstream jet contributing to upward motion over the landmass by means of its thermally direct circulation at its jet entrance. The upstream jet during Type-N events induces downward motion over the southern half of South Africa as it propagates eastward. The Type-S upstream jet streak, which only appears during winter, has limited zonal extent and does not induce downward motion over the country. Type-N ridging is associated with stronger ageostrophic moisture fluxes along the southern coast leading to higher moisture content and precipitation along the south eastern and eastern coasts of South Africa. en_ZA
dc.description.department Geography, Geoinformatics and Meteorology en_ZA
dc.description.librarian hj2021 en_ZA
dc.description.sponsorship The Water Research Commission, South Africa en_ZA
dc.description.uri en_ZA
dc.identifier.citation Ndarana, T., Rammopo, T.S., Reason, C.J.C. et al. 2022, 'Two types of ridging South Atlantic Ocean anticyclones over South Africa and the associated dynamical processes', Atmospheric Research, vol. 265, art. 105897, pp. 1-19. en_ZA
dc.identifier.issn 0169-8095 (print)
dc.identifier.issn 1873-2895 (online)
dc.identifier.other 10.1016/j.atmosres.2021.105897
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2021 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Atmospheric Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Atmospheric Research, vol. 265, art. 105897, pp. 1-19, 2022. doi : 10.1016/j.atmosres.2021.105897. en_ZA
dc.subject Ridging highs pressure systems en_ZA
dc.subject Jet streaks en_ZA
dc.subject Rossby wave packets en_ZA
dc.subject Ageostrophic moisture fluxes en_ZA
dc.title Two types of ridging South Atlantic Ocean anticyclones over South Africa and the associated dynamical processes en_ZA
dc.type Preprint Article en_ZA

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