Quantifying rainfall seasonality across South Africa on the basis of the relationship between rainfall and temperature

Sarah J. Roffe, Jennifer M. Fitchett, Christopher J. Curtis

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

South Africa spans the subtropics at the interface between tropical, subtropical, and temperate weather systems, and consequently experiences distinct summer-, winter- and year-round rainfall zones (SRZ, WRZ and YRZ). Spatio-temporal characteristics of the various weather systems are broadly understood, however, the rainfall seasonality classification at the transition between these rainfall zones remains disputed. This surrounds the complexity of rainfall regimes, however, metrics with dissimilar rainfall seasonality definitions have been applied, hindering comparability. To address this dispute, meteorological data spanning 1987–2016 from 46 weather stations is used to assess the utility of a metric posited to quantify rainfall seasonality through a seasonality score derived from a ratio of monthly rainfall: temperature. This score statistically discriminates SRZ, WRZ and YRZ conditions, fulfilling an important requirement for a metric applied to South Africa. Nelspruit (NEL; score = 1.59) represents the strongest SRZ conditions across 30 eastern and central locations with scores > 0.30. Cape Town Wo (CTW; score = − 1.04) represents the strongest WRZ conditions across seven southwestern Cape and west coast locations with scores < − 0.30. Characterising the SRZ-to-WRZ transition region with scores from − 0.30 to 0.30, nine YRZ locations were classified. With the weakest score, Oudtshoorn (OUD; score = − 0.05), within the Cape Fold mountains, most represents YRZ conditions. Applicability across all weather stations, compatibility with known rainfall drivers, and agreement with known spatial rainfall seasonality characteristics demonstrates the ratio’s utility. Strong correspondence of scores between station and gridded data applications demonstrates additional confidence in the ratio, establishing its value for further application.

Original languageEnglish
Pages (from-to)2431-2450
Number of pages20
JournalClimate Dynamics
Volume56
Issue number7-8
DOIs
Publication statusPublished - Apr 2021

Keywords

  • Rainfall seasonality metrics
  • Seasonality score
  • South Africa
  • Summer rainfall zone
  • Winter rainfall zone
  • Year-round rainfall zone

ASJC Scopus subject areas

  • Atmospheric Science

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