Minister Sonjica launches Mthatha Radar

16 Jul 2010

On 16 July2010 Minister of Water and Environmental Affairs, Buyelwa Sonjica, launched a new state- of-the art weather radar system and handed over a project sponsored by the South African Weather Service to refurbish the Highbury Junior Secondary School in Mthatha. The event took place at the Highbury Community, Mthatha Eastern Cape. The launch of the Mthatha radar system coincided with SAWS’s celebration of 150 years of service to South Africans that will officially be celebrated on 26 October 2010.

The new weather radar network of the South African Weather Service (SAWS) forms part of government’s infrastructure investment to upgrade and replace current weather radars that are over 30 years old. At the official launch of the new South African Weather Radar Network on 29 March 2010 Minister Sonjica mentioned that SAWS is now capacitated with state-of the art weather radar systems around the country, that will bring about a substantially improved weather observation network that meets contemporary needs. The new weather radars will play a vital role in enhancing adaptation tools and products such as the Severe Weather Forecast project and the Flash Flood Guidance System that minimise loss of life and damage to property in events of severe weather.

Weather radars are situated mostly towards the Eastern parts of South Africa, where severe weather is more frequently experienced. Most of the radar systems currently deployed are remote and sometimes inaccessible. The Mthatha radar is unique in the sense that it is located right in the middle of the Highbury community.

The older radar system, which has been operational since 2004, monitors the activity over a critical area of the country prone to natural disasters that often go unnoticed by the general public. The safety and operability of this radar is of paramount importance.

As members of the community are the source of security and sometimes maintenance for the radar site, this has led to the creation of four sustainable jobs and the generation of consistent income for the community. Furthermore, as part of its social development mandate, SAWS has investigated ways of contributing towards the development of this rural district community. With the assistance of community leaders, SAWS embarked on the upgrading of the Highbury Junior Secondary School in Mthatha. With the support of SAWS staff in Mthatha, East London and Port Elizabeth, as well as a subcontractor, SAWS completely refurbished the two existing classroom blocks. SAWS also sourced additional funding to build an additional classroom and ablution facilities, while making use of labour from the local community. Even though SAWS is in the business of meteorology, it can never be separated from its responsibilities to the nation in helping to nurture future generations.

Weather radar systems are particularly useful for the identification of small scale weather systems that are sometimes not clearly visible from weather satellite imagery. This sophisticated instrument senses certain weather phenomena remotely, observes cloud development and motion and can accurately measure the movement of clouds over a radius of approximately 300 kilometres. The position of clouds and weather is displayed on a monitor and analysis of this information assists weather forecasters to provide accurate information and weather warnings to the public. Weather radar systems can provide now casting information on flash floods and tornadoes.

Radar information is captured, monitored and displayed with the information from other radars in the country. This allows forecasters to have a full picture of cloud information over most parts of the country. Cloud information from radars is used in conjunction with other forecast products, weather satellite imagery and measured rainfall in order to gain detailed understanding of approaching weather systems.

Apart from forecasting, research applications are also developed from radar information to benefit agricultural studies, water resource management and the public warnings of approaching severe weather.

Weather radar is a remote sensing instrument using microwave energy between X-band (3 centimeters wave length) and S-band (10 centimeters wavelength). A short pulse of high power microwave energy is produced by a magnetron in the transmitter system and this energy is focused by an antenna system into a narrow beam. This pulse of energy travels through the atmosphere at the speed of light (3 x 10 ⁸ ms^-1).

When a target such as a raindrop is encountered, some of the energy is scattered of which a minute fraction is in the direction back to the antenna system were a sensitive receiver system is used to process and amplify this received power into useful data. From the azimuth and elevation information on the pointing direction of the antenna, the time between transmitting and receiving and the power of the received signal, the target location can be determined as well as its intensity or reflectivity.

Various atmospheric and environmental conditions can negatively affect radar data and caution should be exercised when interpreting the information. Some of these effects include:

• returns from mountains and other non-meteorological targets
• attenuation of the radar signal when viewing weather echoes through areas of intense precipitation(with C-band radars)
• temperature inversions in the lower layers of the atmosphere which bend the radar beam in such a way that ground clutter is observed where normally not expected
• the "bright band" which is a layer of enhanced reflectivity caused by the melting of ice particles as they fall through the O^oC level in the atmosphere and which can result in over-estimation of rainfall.

Fore more information contact:
Ms Modjadji Makoela
Tel: 012 367 6055
Cell: 084 361 6469

Issued by: Department of Environmental Affairs
16 Jul 2010