Establishment of the South African baseline surface radiation network station at De Aar

Abstract

The South African Weather Service (SAWS) was offered a unique opportunity to become involved in the prestigious global Baseline Surface Radiation Network (BSRN) project in 1995. This study is an academical and technical document describing and elucidating aspects regarding the eventual establishment of the BSRN measurement facility at De Aar that embodies South Africa’s involvement. The dissertation opens with an introductory chapter offering background information and an explanation of circumstances leading to South Africa’s involvement in this project, including reasons exactly why De Aar was chosen to be the South African BSRN site. This is followed by details on a scientific measurement plan including necessary information on radiation processes in the atmosphere, measurement techniques and associated instrumentation. The next chapter is devoted to the design of a radiometric measurement system answering to the scientific plan, with more details on instrumentation, peripherals, calibration and data management strategies. Three years of real measured data since station establishment, is used as a basis to apply and evaluate the various quality assurance techniques of the central BSRN data-archive. Special reference is made in a separate chapter to the two partial solar eclipses that traversed Southern Africa in 2001 and 2002, in the form of case studies. This dissertation is illustrated by several photos, and rounded off by details of the station-to-archive file format as laid down by the international BSRN data-archive, a useful table reflecting sunrise, sunset, solar transit, day length and Top Of Atmosphere (TOA) radiation, an explanation on climate zone classification, as well as a useful technical guide on setting up a pyrgeometer. Apart from the academic content this document also intends to serve as a guideline for station operation and future development of whatever form, for both the station scientist and the station manager. Such developments can include the establishment of other BSRN stations, or in general the enhancement of the quality of solar radiation measurements over the entire Southern Africa Developing Community (SADC) region. The author wishes to state that in presenting this document in English, he does not wish to promote English as scientific language at the expense of Afrikaans. The choice of language was taken purely on the basis of broader international involvement and a wider local usefulness of this document.