The analysis of tropical temperate trough-associated rainfall onsets and their influence on maize yields in the Maize Triangle, South Africa

Abstract

Tropical temperate troughs (TTTs) that were associated with rainfall onsets in the Maize Triangle, South Africa, were analysed during the period from 1979 to 2018. Maize yields for agricultural regions within the Maize Triangle were also investigated to determine if the association of the above-mentioned variables had any influence on their trend. Various datasets which included observed TTT cases, daily rainfall, outgoing longwave radiation (OLR) and maize yields were obtained from various providers. These datasets were processed, merged and analysed accordingly using various tools and methods to address the study objectives. The study analysed the climatology of TTTs over southern Africa and found that their activity is highest during the early period of the rainy season (September to November), when the Intertropical Convergence Zone (ITCZ) is at its lowest latitude, and they retreat mid-season while the significantly disappear during the latter part of the season. The study found that almost all rainfall onsets were associated with TTTs, implying the importance of TTTs, particularly for early rainfall onsets in the study area. The study also found that early occurring TTT-associated rainfall onsets were responsible for much of the rainfall that was concentrated over the eastern parts of the Maize Triangle while that which occurred mid-season was almost evenly distributed over the study area. Final analysis indicated that maize yields were not affected by subsequent TTT-associated rainfall onsets which can be attributed to the large number of non-meteorological activities that occur during the planting, growing and harvesting periods.