选取位于东部沿海的高邮、新沂、陵阳、昌黎4个台站2011年全年12个月的地电场分钟值观测资料，利用小波变换法计算其半日波，与位于内陆的大同、石嘴山、古丰台进行对比，分析沿海地区地电场半日波日变幅的变化规律，研究得到：①高邮等4台在2011年部分月份单月发生2次半日波日变幅增大、减少的现象，同一台站不同月份此现象的发生时间几乎一致（阴历日期），不同台站同一月份此现象的发生时间不同，而位于内陆地区的地电场台站未观测到此现象。②通过研究台站测区及周围环境与半日波日变幅变化的相关性，初步分析认为位于沿海地区的台站是否容易观测到半日波日变幅周期性变化可能与测区是否紧邻大型水系有关；而位于沿海地区的台站观测到地电场半日波日变幅每月2次增大、减少的发生时间可能与台站的地磁经度有关。③探讨了引起东部沿海地区半日波日变幅周期性变化的可能原因。

In this paper,the minute data observed from January to December 2011 by Gaoyou,Xinyi,Lingyang and Changli electric field stations in eastern inshore areas of Chinese mainland were processed via the wavelet transform,and were compared to the Datong,Shizuishan and Gufeng stations in the inland areas. We analyzed the change of amplitudes of semidiurnal variation. The results showed that:(1)The phenomenon of the increase and decrease of diurnal variation amplitude of semidiurnal wave occurs twice for each month in part of months in 2011 at Gaoyou,Xinyi,Lingyang and Changli electric field stations. This phenomenon in different months at the station occurs almost in the same time(lunar calendar date)and in the same month at different stations occurs in the different times,but the stations in the inland areas didn't observe the phenomenon. (2)The relationship between the condition of stations in measured area and this phenomenon is studied. A preliminary conclusion is drawn that this phenomenon has connection with the river drainage systems in measured area and near. The occurrence time of this phenomenon may be associated with the magnetic latitude of the stations. (3)The possible cause of this phenomenon is discussed.

P315

国家自然科学基金（41374080）资助