P5.2 Doppler radar for adverse weather surveillance and warnings in Botswana

Monday, 6 August 2007
Halls C & D (Cairns Convention Center)
Sacrasta Nchengwa, Department of Meteorological Services, Gaborone, Botswana; and D. Thebeetsile, J. Selato, D. B. Michelson, and D. E. Terblanche

This contribution symbolizes the necessity and application of Doppler radar for observing severe weather over Botswana, as and when it occurs, so as to enable well-timed issue of relevant warnings to the public. Botswana lies in the subtropics and, as such, most of its rainfall is largely convective by nature, and therefore poses a serious challenge to weather forecasters.

The convective rainfall brings thunderstorm activities that often give rise to severe weather across the country during the rainfall season. Severe weather drives many of the most devastating natural disasters known to humanity. These weather driven disasters can vary in type, cause and impacts, and very so often affect human life in many ways. Therefore, critically important for weather forecasters is to be able to observe and detect severe weather events in order to mitigate their potential negative impacts on society.

One of the many technologically refined tools often employed to observe weather is the weather radar. It has many vital functions, one of which is in helping to track and detect the fast-developing convective storms which could normally be difficult to forecast in terms of their genesis, growth, strength and movement.

In this way, the radar becomes useful as a warning tool for impending weather disasters and therefore aid in minimizing the impact of hazardous weather on human lives. Its goes without saying that well-functioning and fully-operational weather radar provides the users with quality data that can help in tracking and detection of hazardous weather as and when it occurs.

Botswana Meteorological Services has been operating a Doppler radar for the past four years as part of its weather-observing network. An EEC DWSR-8500S Doppler radar was chosen since Doppler radars are necessary for measuring radial velocity, and observing the structures of tropical cyclones, hurricanes and other violent storms which could put peoples' lives at risk. S-band radars are not significantly affected by signal attenuation and they give a useful range with less velocity folding than higher-frequency radars. The Botswana radar has a maximum range of 250 km (in Doppler mode) and is located at Bokaa, some seven km north east of Sir Seretse Khama International Airport outside the capitol of Gaborone.

Plans are in the works to acquire at least two more radars to create a radar network of for Botswana. This network will be integrated with satellite receiving systems, message switching systems and data management systems in line with proposals made in a project between the Swedish Hydrological and Meteorological Institute and Botswana Meteorological Services. The Bokaa Doppler radar is currently integrated with the South African Weather Service radar network.

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