A glimpse at the 17th century Cape climate of Southern Africa: documentary based evidence from the Jan van Riebeeck diaries

Abstract

The diaries of Jan van Riebeeck contains one of the oldest documentary records of weather phenomena for the southwestern Cape. They contain descriptions of daily wind direction and strength and daily rainfall events. The primary aim of this research is to reconstruct a comprehensive weather chronology for the southwestern Cape region from these diaries, spanning the period 1652-1665, and place this in context with the 20th-21st C climate for the region. The study further aims to examine the relationships between the 17th C society and natural environment. All climate and environmental information is extracted from the diaries and tabulated. Qualitative information on wind and rain was classified and transformed into quantitative data. Contemporary data retrieved from the Royal Observatory and the South African Weather Services are used to make comparisons between the historical study period and contemporary conditions. However, due to the qualitative nature of the historical data, statistical analysis demonstrated that such comparisons are limited. Within the historical period, analysis of the number of rain days demonstrated a distinct wet period in the first half followed by progressive drying. Wind data from the diaries reflected distinct seasonality linked to shifts in the position of the ITCZ. Additionally, unusual events including snow, hail, the Black south-easterly and ‘dirty rain’ are explored. Qualitative data revealed a heavy reliance on climate to support crops and livestock, and a range of environmental stresses to human health, infrastructure and food security.