大辽河口存留时间和暴露时间数值模拟

为了研究河口的物质输运机制,采用一个基于有限体积海岸海洋模式(FVCOM)的三维对流-扩散模式对大辽河口5个分区典型径流条件下的存留时间和暴露时间进行计算,得到了示踪物从河道第1次输送至入海河口的时间,以及随后返回河道里往复运动的时间,并据此统计得到回复系数以及表征各个分区之间相互影响的分区暴露时间矩阵。结果显示:潮汐、径流之间的相互作用控制着大辽河口的存留时间;暴露时间与存留时间的变化趋势一致,但大小差别很大,在枯、平、丰水期,暴露时间比存留时间分别多8 d、3 d、1 d;枯水期入海口河段回复系数可以达到0.94,示踪物会在这个区域多次回荡;除了涨急时刻的入海口河段,其他情况下大辽河下游分区对上游分区影响较小。

Numerical study of residence time and exposure time in Daliaohe Estuary

To study the mass transport process in an estuary,residence time and exposure time were calculated for five boxes in Daliaohe Estuary in three typical runoff conditions using a three-dimensional convection-diffusion model based on Finite-Volume Coastal Ocean Model(FVCOM).Data were obtained for both the time required to leave the control domain for the first time and the total time spent in the control domain.Then,the return coefficient and the subdomain exposure time matrix which show the interaction between boxes were also investigated.The results showed the interaction between the runoff and tides control the residence time in Daliaohe Estuary.Exposure time and residence time have the same change trendency,but they differ greatly in size.Exposure times are 8,3 and 1 days more than residence times during dry,normal and rainy seasons,respectively.The return coefficient could reach 0.94 at the downstream end during dry season,with the tracer returning to this area many times.The downstream boxes have little influence on the upstream boxes in Daliaohe estuary except for the case in the downstream end at the maximum flood tide.