I have analysed the annual rainfalls at ten stations in South Africa. These are all long-term records with data from as far back as 1850 (Capetown) and all stations have data up to 2017.
The only data that I have been able to locate is that on the KNMI (Royal Netherlands Meteorological Institute) website.
The earliest record is at Capetown (Royal Observatory) where data are available since 1850. The KNMI data does not continue since 2000, although it is known that data since then exists (the station has been renamed SA Astronomical Observatory). Attempts to obtain data for this station since 2000 from SAWS (South African Weather Service) and UCT (University of Capetown) have been unsuccessful. Accordingly, data from the nearby International Airport were used for the period since 2000. Annual totals (Nov-Oct), in the form of graphical plots, were also found at SA Astronomical Observatory for seven years since 2000 and these values have, in the absence of any other data, been included in the analysis. https://briangunterblog.wordpress.com/2018/02/14/capetown-rainfall/
Overall the data availability at the ten stations is good, except during the past 20 years when there are many months of missing data at all stations. This is most unfortunate, particularly in view of the current drought that is affecting some areas of South Africa. An extreme example is the record at Pretoria which had only one incomplete year of data between 1920 and 1999 but has no complete years of data since then:
The following are plots of the annual (Jan-Dec) rainfalls at each of the ten stations. The red line is of the five-year average rainfall.
Capetown 1850-2017 (Nov-Oct)
Port Elizabeth 1872-2016
East London 1900-2016
Polokwane (Pietersburg) 1909-2017
The ten selected long-term rainfall stations are representative of South Africa, except in the east where no data were available.
The data availability is good, except for the most recent 20 years when there are many missing months of data at all stations.
For Capetown a more detailed analysis was carried out, involving the amalgamation of historical records from three nearby stations. This resulted in a unbroken record of rainfall at Capetown for the 168 years, 1850-2017.
At all stations there is a relatively constant trend in annual rainfall until around 2000.
After around 2000 the lack of complete data makes it impossible to determine the long-term trend.
There is an indication that the period since around 2000 may have had lower than normal annual rainfalls in the south of Western Cape province (Capetown, George), but additional data are required to determine this with any confidence.
The available data at the other eight stations show no conclusive evidence of abnormal drought in the past decade.
Please let me know what you think of my analyses. firstname.lastname@example.org
This article was written by Brian Gunter of Narooma, NSW, Australia. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Bureau of Meteorology.