瓯江口内外潮汐不对称研究

A study of tidal asymmetry in Oujiang estuary

基于对瓯江口内外2005年6—7月多个潮位站15 d的实测潮位资料分析,利用3种方法研究了瓯江口潮汐不对称现象及其在时空上的变化特征与机理.研究认为,在理论上传统地采用M2与M4分潮的相对振幅判断潮汐不对称的方法不完善,潮汐不对称不仅受到相对振幅的影响,而且受到其相对位相的影响,同时其他分潮的相互作用也是导致河口、近岸潮汐不对称的重要因素.瓯江口潮汐属正规半日潮,潮汐不对称的产生主要是由于M2分潮及其倍潮M4的相互作用.潮汐不对称的空间变化主要表现在沿河道的纵向上,即潮汐在纵向上由口外向上游不对称逐渐增强.在横向上,口门外由于地形开阔,水深较大,潮汐不对称不明显且无明显变化趋势.在时间上,潮汐不对称在大-小潮期间具有明显变化,表现为大潮期最为明显,远大于小潮期.因此可以认为潮汐不对称在大-小潮期间的变化是低频分潮Msf分潮所致.

Based on the fortnight measured tidal elevation asymmetry, and its time-space variation are studied by three in June-July 2005 in the Oujiang estuary, the tidal methods. The research results show that the traditional method of determining tidal asymmetry just by the relative amplitude of M4 and M2 is not perfect in theory. The relative amplitude and the relative phase as well as other constituents would affect tidal asymmetry in combination. Tides in the Oujiang estuary are the semidiurnal tides. M4 plays the most significant role in the tidal asymmetry. Longitudinal variation is more obvious than the lateral one. The tide distortion becomes greater from the fiver mouth towards upstream. It is relative weak and has no marked tendency to variation outside the month due to large spatial scale and water depth. Temporally, the tidal asymmetry is considerable during spring and neap tides and more remarkable during the spring tides than neap tides because of the Msf. And as it may be seen from the analysis above the tidal asymmetry variation during the spring and neap rids must be caused by the constituents of the Msf.