Operational weather radar networks in Africa: A South African case study

Africa is prone to severe weather conditions ranging from hail storms to cyclones, all with devastating effects on a countries economy and infrastructure. Remote sensing instruments, like radar, provides the opportunity to observe large areas with a minimal infrastructure footprint. In the past millions of dollars have been invested in building radar capacity in Africa, however this have been mostly unsuccessful since Africa presents certain challenges not always considered. This presentation will evaluate the use of weather radar in South Africa as an example of how the challenges could be faced. South Africa has a long history in weather radars as it was at the forefront of radar development and use since the early 40's. In more recent years the South African Weather Service (SAWS) invested roughly $20 million on upgrading and expanding its radar network with high quality radars from Gematronik (now Selex ES). These included 10 S-band radars, one of which is a research-grade dual-polarized unit situated in Bethlehem, and 2 mobile X-band research radars giving a total of 16 radars. Even with all the experience gathered over the years and investing millions of dollars, the SAWS are plagued by technical problems. A drastic shift towards commercial operation enforced by legislation and dwindling funding has severely limited capacity and resources dedicated to the national weather radar network.

Due to the lack of technical expertise and funding, a recent study done by the SAWS has shown that only 54.3% of the radar data collected for the past 12 month period are available. Some of the radars including the dual-polarized radar in Bethlehem are not properly calibrated resulting in inaccurate data. The SAWS manages 230 Automatic Weather Stations (AWS), 130 automatic rainfall stations (ARS) and 24 lightning detection sensors (LDS).

In spite of the fact that the SAWS has the most advanced radar systems in Africa it struggles to keep the radars operational. Another example of two countries with the same scenario are Mozambique and Botswana, both with advanced radars that are not being maintained. Nevertheless it is crucial for Africa that weather radars are deployed throughout the continent in a more effective manner. According to the Southern Africa Development Community (SADC) one of their highest priorities is the strengthening of observation networks including the expansion of radar networks.

The Potchefstroom campus of the North-West University (NWU), South Africa is building capacity in radar meteorological research and engineering through innovative methods. In 2014 the NWU acquired an outdated old WSR74C EEC weather radar from Cotulla, Texas with the purpose to re-engineer the radar to a research standard dual-polarization radar. The re-engineering process consists of upgrading the original radar to dual-polarization using off-the-shelf components. This method will help keep the upgrade cost to a minimum and provide much needed technical skills to understand, maintain and expand the radar network. Since most of the components will be locally sourced it will keep the maintenance cost and radar downtime to the minimum.

It is well known that weather radars involve certain risks. Over the years as the technology improved the reliability of radars improved immensely. Yet, globally there are many radars still using previous generation technology. This presentation will focus on some of the risks involved in operating a single radar and linked in a network.

One of the first and important steps in re-engineering the NWU's radar is to conduct a thorough risk assessment on the radar system. It is imperative that all the risks associated with a radar system are known. The risks assessment includes topics such as the re-engineering process, overall cost, infrastructure, communication network, maintenance and feasibility of the project. The assessment strongly focuses on the re-engineering process to better understand why it is difficult to maintain a radar network in Africa or other developing countries. An example of one of the risk assessment is the risk of each internal component, their probability to fail and the cause and effect on the system. Knowing which components have a higher risk value allows the engineer to focus on lowering that specific component's risk and so improve the systems overall reliability.

It is important for each country to not only observe its weather but keep doing research to help better understand weather phenomena's and the effect of climate change. It is vital that developing countries in Africa also contributes to meteorology and engineering fields to the best of their capability. However developing countries are facing challenges including access to specialized parts, lack of local capacity and support and the lack of funding for human resources and basic maintenance. International donor funding is usually earmarked for infrastructure development but there is a dire need for continued funding for technicians, engineers and scientist to keep the radars working and develop products of interest to local stake holders.

A new strategy is needed to rather upgrade less expensive radars and keep the network operational than having the best radars available but not able to keep it operating. Re-engineering decommissioned radars using off-the-shelf technologies is a viable means of expanding networks in Africa with limited funds while growing local capacity and contributing to society.