Attributes of cut-off low induced rainfall over the Eastern Cape Province of South Africa

• Published in: Theoretical and applied climatology 2014-10, Vol.118 (1-2), p.307-318
• Main Authors: Molekwa, S, Engelbrecht, C. J, Rautenbach, C. J. deW
• Format: Article
• Language: English
• Subjects: Analysis; Aquatic Pollution; Atmospheric circulation; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; autumn; Climate science; Climatology; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Hydrologic data; meteorological data; Meteorology; Original Paper; rain; Rain and rainfall; Rainfall; Rainfall measurement; Spatial distribution; spring; summer; Temperature; Waste Water Technology; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Water Management; Water Pollution Control; Winter
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-013-1061-3

Cut-off low (COL) weather systems that are associated with rainfall over the Eastern Cape are considered in this study. COLs are objectively identified and tracked over a 31-year period. Daily rainfall data of 22 evenly distributed stations over the Eastern Cape are utilized. Only COLs with a minimum spatial distribution, defined as more than a third of the rainfall stations that need to report rainfall on at least 1 day of a COL event, are considered for analysis of rainfall attributes. These attributes include the occurrence of COL rain days of different magnitudes, the distribution of the depth and temperature of the COL centres for the rain days of different magnitudes, the associated spatial distribution of rainfall as well as the associated atmospheric circulation. The frequency of COLs over the Eastern Cape has a winter maximum and a summer minimum. COL rain days of small, medium and large magnitudes occur most frequently during the winter, while small- and medium-magnitude COL rain days experience peaks in autumn and spring, respectively. The low-level flow, and in particular the position of the low/trough, seems to be the determinant factor in the occurrence, magnitude and spatial extent of COL-induced rainfall.