长江河口潮位站潮汐特征分析

基于横沙、马家港、堡镇和永隆沙4个潮位站2009年实测的逐时水位资料，分析了长江河口潮位站潮汐的时空变化特征、分潮组成、潮汐类型和变形.长江河口潮位站的潮汐存在日不等现象，主要表现为高潮位不等，其中3月份、9月份期间的日不等现象小潮比大潮明显，而6月份、12月份期间则是大潮比小潮明显.统计给出了潮位站各月最大潮差和最小潮差，长江河口的潮差呈现双峰变化，月最大潮差在3月份、9月份出现极大值，6月份、12月份出现极小值；月最小潮差在6月份、12月份出现极大值，3月份、9月份出现极小值.受径流和摩擦等影响，在南支向上游潮差减小.因北支径流分流比小，且地形呈喇叭口状，使得永隆沙站潮差比其他3个潮位站大.长江河口潮汐主要由4个主要半日分潮（M ₂、S ₂、N ₂、K ₂ ）、4个主要全日分潮（K ₁、O ₁、P ₁、Q ₁）和3个主要浅水分潮（M ₄、MS ₄、M ₆）组成.半日分潮占绝对优势，受河口水浅的影响，浅水分潮显著.潮汐类型系数除了永隆沙站小于0.25，其余3站的均大于0.25，表明北支属于正规半日潮，而北港、南港和北槽则属于不正规半日潮.4个测站的潮汐变形系数均大于0.1，表明长江河口潮位站潮汐变形显著，其中以北支永隆沙潮汐变形最为严重，变形系数可达0.173.

Analysis of tidal characteristics of the tide gauges in the Changjiang Estuary

Based on the measured water levels at Hengsha,Majiagang,Baozhen and Yonglongsha tide gauges in 2009,the tidal temporal and spatial variations,tidal constituents,tidal form and distortion at these gauges in the Changjiang Estuary were analyzed.There exist tidal daily inequalities that mainly occur during high tide levels,and are more significant during neap tides than spring tides in March and September while are more significant during spring tides than neap tides in June and December.The monthly maximum and minimum tidal ranges in each month at the tide gauges were given out statistically.The tidal range in the estuary varies monthly with two peaks;the maximum tidal range reaches the maximum values in March and September, and reaches the minimum values in June and December.The minimum tidal range reaches the maximum values in June and December,and reaches the minimum values in March and September. The tidal range in the South Branch reduced toward upstream due to the river discharge and friction.The tidal range at Yonglongsha tidal gauge is the largest among the 4 tidal gauges because the North Branch has small river discharge division ratio and funnel shape bathymetry. The tide is mainly composed by the 4 semi-diurnal tidal constituent（M₂,S₂,N₂,K₂）,4 diurnal tidal constituent（K₁,O₁,P₁,Q₁ ） and 3 shallow water tidal constituent（M₄,MS₄,M₆）. The semi-diurnal tidal constituents M₂ and S₂ are the predominant ones,and the shallow water tidal constituents M₄ and MS₄ are apparent due to the shallow water in the estuary.The tidal form number in the South Branch is larger than 0.25,indicating where the tide is an irregular semi-diurnal tide type there,and is smaller than 0.25 in the North Branch,indicating where the tide is a regular semi-diurnal tide type.The tidal distortion coefficients in the 4 tidal gauges are all larger than 0.1,indicating that the tide at the tide gauges has significant distortion in the Changjiang Estuary,especially at Yonglongsha in the North Branch with tidal distortion coefficient 0.173.