Accessibility navigation

Drylines in Southern Africa: Rediscovering the Congo Air Boundary

Howard, E. and Washington, R. (2019) Drylines in Southern Africa: Rediscovering the Congo Air Boundary. Journal of Climate, 32 (23). pp. 8223-8242. ISSN 0894-8755

Text (Open Access) - Published Version
· Available under License Creative Commons Attribution.
· Please see our End User Agreement before downloading.


It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing.

To link to this item DOI: 10.1175/JCLI-D-19-0437.1


Projected rainfall decline in southern Africa is likely to be highly sensitive to subtleties in the local atmospheric circulation. In an effort to understand the regional circulation complexities, a novel algorithm is developed to identify the Congo air boundary (CAB) in ERA-5, a high-resolution reanalysis dataset. The CAB, a forgotten feature of the circulation, is defined in the austral spring and early summer, using surface humidity gradients and near-surface wind convergence lines, and it is found to be an indicator of the location of the southern edge of the African rain belt. A related convergence-line and dryline feature, described in this paper as the Kalahari discontinuity (KD), is also identified. It is established that either a dryline CAB or KD is present in southern Africa for over 95% of days between August and December, with arc lengths typically exceeding 10°. The seasonal and diurnal cycles of the CAB and the KD are presented, and their prevalence in station observational data is confirmed. The interannual variability of the CAB latitude and detection frequency is found to explain at least 55% of interannual spring rainfall variability in southern Africa between 15° to 25°S. Links are established with the Angola and Kalahari heat lows and tropical temperate trough events.

Item Type:Article
Divisions:No Reading authors. Back catalogue items
Science > School of Mathematical, Physical and Computational Sciences > NCAS
Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:87536


Downloads per month over past year

University Staff: Request a correction | Centaur Editors: Update this record

Page navigation