Developments of authentic annual and seasonal lightning thunderstorm day maps for Saudi Arabia

Lightning is a hazardous phenomenon, and knowledge about spatial distribution of thunderstorms and lightning are of high importance. The derivation of reliable estimates of lightning activity requires statistical averaging over a large area and a considerable number of years of observation. One of the objectives of this original research is to establish and develop the annual and seasonal maps of the Isokeraunic level (Thunder days, Td) for Saudi Arabia. Another objective is to present the steps of development and validation of these authentic maps. The Td is an essential parameter used in the calculation of lightning performance of transmission lines, Alternatively, it may be estimated from Td using empirically derived equations, which is the method adopted in the report for Saudi Arabia since no counters or detection systems are currently in use. A new seasonal and annual thunder day maps for Saudi Arabia are presented. On the basis of these maps, the distribution of thunderstorms over the country is analysed in terms of the development factors required for determining lightning performances of transmission lines. Mapping of lightning strikes collected data was possible by using software developed by the ESRI group known as ArcGIS. Thunder days (Td) in different areas of Saudi Arabia specifically those where lightning strikes are more likely to occur has been determined. Presidency of Meteorology and Environment (PME) is the prime provider of all available data and records available on lightning and thunderstorm incidences in Saudi Arabia that was used in this research. Even though these data were obtained through human observations, it still makes it more authentic than extrapolated from old maps. The present maps indicate the location, and frequency of where lightning will strike, such information is very valuable for the design engineers of the transmission and distribution lines and operation for optimum selection, and insulation coordination of the lightning protection systems. Thunderstorms are more frequent over the southwest of the country, and generally decrease towards the west. Thunderstorm frequency does, in general, appear to vary in a consistent way with rainfall especially in the southern region; however, thunderstorm frequency does not appear to vary in any consistent way with rainfall in the eastern and western regions. There appears to be no evidence of any widespread temporal trend in thunderstorm frequency.