中文摘要：

考虑长江河口径流、潮汐和风场共同作用,数值模拟和定量分析北支潮位和潮差时空变化和动力机制.北支月平均潮位呈现出从1月到7月逐渐增大,从8月到12月逐渐减小的变化趋势,主要决定于径流量产生的余水位.潮差具有季节变化,一年中出现两次极大值和两次极小值.两次极大值出现在3月（农历二月）和9月（农历八月）,两次极小值出现在6月（农历五月）和12月（农历十一月）.青龙港最高潮位和最低潮位主要由潮汐强度决定,也与潮汐季节性变化和径流量有关.北支平均潮位、最高潮位和最低潮位纵向上基本呈现从下游往上游逐渐增加的变化规律,北支的潮差变化呈现出从口门向中段逐渐增大,再从中段向上段逐渐减小的规律.冬季偏北风使青龙港潮位增大,夏季偏南风使青龙港潮位和潮差略微减小,风对北支潮差几乎没有影响.径流产生的余水位增加潮位,径流对潮汐具有抑制作用,使潮差减小.

英文摘要：

With the combined effects of the river discharge,tide and wind stress,the spatial/temporal variations as well as the dynamical mechanism of the tidal level and tidal range in the North Branch of the Changjiang Estuary were numerically simulated and quantitatively analyzed in this paper.The monthly mean tidal level in the North Branch is increased gradually from January to July and decreased gradually from October to December.It mainly depends on the residual water level,which is determined by the amount of the river discharge.The tidal range experiences a seasonal variation,with two maximum and two minimum values in a year.These two maximum values appear in March（the second lunar month） and September（the eighth lunar month）,and the two minimum ones appear in June（the fifth lunar month） and December（the eleventh lunar month）,respectively.The highest and lowest tidal levels at the Qinglonggang station are mainly determined by the intensity of tidal forcing,and associate with the seasonal variations of the tide and river discharge.The averaged,highest and lowest tidal levels represent a landward increment feature along the North Branch.The tidal range is increased gradually from the mouth to the middle reaches of the North Branch,and decreased from its middle reaches to its upper reaches.The northerly wind in winter tends to produce an increment of the tidal level at the Qinglonggang,and the southerly wind in summer tends to produce a slight decrement of the tidal level and range there.The wind stress has almost no effect on the tidal range in the North Branch.The river discharge increases the tidal level,restrains the tide,and decreased the tidal range.