广州市闪电密度特征分析

Analysis of Lightning Density in Guangzhou City

本文利用闪电定位资料和气象台站记录的雷暴日资料，对广州市闪电密度时空分布特征进行了分析。研究表明，广州市位于广东省闪电密度高值区，在5′×5′网格内每年总闪次数在500次-1000次；闪电类型以负闪为主，负闪次数占了总闪次数的96．76％；广州市每年闪电发生季节主要出现在4月-9月，这一时期的总闪次数占全年的96．63％，其中最高值出现在7月，次高值在6月、8月；每天13时～19时是闪电高发时段，这主要与午后出现强对流天气关系极为密切；广州市闪电密度空间分布具有明显的区域性，高值偏西和偏南，主要位于广州市偏西的越秀区、荔湾区和偏南的番禺区北部；各月正闪电流强度高于负闪电流强度，并且电流强度高值区与闪电密度高分布区基本一致，这一区域更要重视防御雷电灾害。

With daily dataset of thunderstorm measured with lightning locators and weather stations, the temporal and spatial distribution of lightning density in Guangzhou is studied. It is found from distribution of lightening across the Guangdong province that there are areas of high total CG lightening and return strokes over the Pearl Rive Delta, Qingyuan and Lianjiang during 2000 - 2003. The city of Guangzhou is within the two high-lightning areas, with an annual total between 500 and 1000 times of lightning for a mesh of 5′ × 5′ over the 4-year period. There are as many as 20 times of lightening in the two areas and between 10 and 16 times of lightening in Guangzhou per year per km^2 . The period also witnesses a much higher frequency of lightening per km^2 in the two areas than in other areas. The lightning is mainly of negative CG strokes, which takes up 96.76% of the total. Frequent lightening occurred in 2000 and 2002. In Guangzhou, lightning mainly occurs from April through September, which is 96.63% of the annual total. The most frequent month is July, followed by June and August. The number of lightening in July and August takes up 25 % and 22 % of the annual total respectively. The most frequent period of a day is between 13：00 and 19：00, which is closely associated with severe convection weather taking place after the midday. The spatial distribution of lightning is regional wise, with the dense area being in the western and southern parts of the city. It is attributed to both increased urban roughness, which blocks and lifts the air flowing above the city, and the migration of thunder storm systems in summertime from the west or southwest. It is also found in the study that on the monthly basis, the electrical current is very intense with positive CG lightning than with negative one and high current intensity is always with highdensity distribution. For the region, more attention should be paid to disasters caused by lightning.