基于FBM法追踪秦皇岛海域赤潮迁移扩散

在Delft3D-FLOW模型模拟水动力的基础上，基于FBM粒子追踪法建立和验证赤潮迁移扩散模型.模拟了秦皇岛海域潮流和风生流，分析了风生流对赤潮迁移扩散的作用，对比分析了FBM法、拉格朗日法和常规布朗运动法在赤潮迁移扩散模拟中的特性，测试了模型Hurst指数的敏感性并得出其在赤潮模拟中的合理取值范围.主要结论为：①秦皇岛海域的赤潮主要随潮流的涨落而往复移动，一个涨落潮周期内赤潮的净迁移距离较小；②秦皇岛海域夏季潮流较弱，但风对赤潮迁移具有一定影响，易产生东北向风生流，导致赤潮更易往东北方向迁移；③Hurst指数较明显地影响粒子云的扩散范围，Hurst指数取0.80±0.03能比较真实地模拟秦皇岛海域赤潮的迁移扩散；④FBM法可模拟赤潮的non-Fickian扩散现象，使其模拟的粒子云扩散范围和分布形状明显优于拉格朗日法和常规布朗运动法.

Tracking migration and diffusion of red tides in Qinhuangdao coastal water based on FBM method

Based on the hydrodynamic simulation by Delft3D-FLOW, the model of migration and diffusion of red tides, based on the FBM (Fractional Brownian Motion) particle tracking method, was established and validated. The flow and wind-driven current in Qinhuangdao coastal water were simulated, and the effects of wind-driven current in migration and diffusion of red tides were presented. The characteristics of the FBM method, Lagrange method and the conventional Brown method in simulating migration and diffusion of red tides were compared. The sensitivity of Hurst index in the model was analysed, and its reasonable range in simulation of migration and diffusion of red tides was obtained in Qinhuangdao coastal water. Main conclusions were:1) red tides migrated in Qinhuangdao coastal water with reciprocating tidal currents, resulting in a small net migration distance of red tides during an entire flood and ebb period; 2) the tidal current in Qinhuangdao coastal water was weak in the summer, but the wind-driven current in the northeast direction resulted in the red tide being transported northeastwardly; 3) Hurst index could significantly affect the diffusion range of particle cloud, Hurst index in the range of 0.80±0.03could more accurately simulate migration and diffusion of red tides in Qinhuangdao coastal water; 4) FBM method could simulate the non-Fickian diffusion phenomenon of red tides, which made the diffusion range and shape of the particle clouds closer to the actual situation than those using the Lagrange method and the conventional Brown method.