Investigation About The Influence Of Tall Structures On Cloud-to-ground Lightning In Their Vicinities In Guangzhou

Zhujiang New Town is the main component of the Guangzhou Tianhe Central Business District,which has crowded tall structures with heights over 300 m,such as the Canton Tower(600 m high),Guangzhou International Finance Center(GIFC,440 m high),and Guangsheng Building(GS Building,360 m high).The three tall structures were selected as the study objects.This paper analyzed the cloud-to-ground(CG)lightning characteristics in the vicinities of tall structures,based on data obtained by Lightning Location System(LLS)of the Guangdong Power Grid Corporation from 1999 to 2015.The lightning characteristics in the vicinities of tall structures obtained before(1999-2005)and after(2010-2015)the erection of the three tall structures were compared.The conclusions were as follows:1)The influence of the Canton Tower on CG lightning in its vicinity were analyzed by comparison the lightning characteristics before and after the erection of the Canton Tower and the results showed that:Compared with the arithmetic mean value(AM value)within 10 km radius of Canton Tower(40.2 km-2yr-1 and 20.0 km-2yr-1),the stroke and flash densities in the immediate vicinity around the Canton Tower within radius of 1 km(51.4 km-2yr-1 and 29.1 km-2yr-1)showed a significant increase,and a clear decrease in the annular vicinity within radius from 1 km to 4 km(34.4-37.2 km-2yr-1 and 18.2-19.5 km-2yr-1).The AM value of the LLS-inferred peak current of strokes occurred in 1 km radius area around the Canton Tower(47 kA)exhibited a significant increase,compared with the AM value within 10 km radius(29 kA),while that of the lightning occurred beyond 1 km did not show a clear change.The percentage of negative flashes(ratio of negative flashes to total flashes)showed a slight increase in the immediate vicinity around the Canton Tower,which could be caused by the upward lightning(often negative)initiated from the tower.Due to the existence of the Canton Tower,the lightning multiplicity presented a decrease trend to some extend within 4 km radius around the tower compared with the AM value within 10 km radius.It is speculated that the Canton Tower induced lots of upward flashes and attracted some downward flashes around it within several kilometers radius to itself.2)According to analyzed the characteristic of strokes distribution within 1 km radius of the Canton Tower,a systematic location error of the GDLLS in stroke location detection was found in the area of Zhujiang New Town.The strokes distribution for Canton Tower GDLLS detected strokes can also prove this systematic location error.It seems that the stroke locations detected by the GDLLS were about 170 m to the east and 150 m to the south,compared with the exact locations.3)A more detailed analyses about the lightning characteristics in the vicinities of Canton Tower,GIFC,GS building were presented in this paper,after the correction of the systematic location error.The results showed that:The increase influence range of the Canton Tower on stroke density was accurate to within 0.5 km of the tower.The increase influence of the Canton Tower was obvious larger than that of GIFC and GS building and increase influence range of the Canton Tower was slightly widespread than the other two buildings.With the height increase of a tall structures,the increase effect of tall structures on AM value of the LLS-inferred peak current in their immediate vicinities would be enhanced.