Numerical simulation on storm surge caused by extratropical cyclone in Bohai Sea,China

Based on three-dimensional nonhydrostatic mesoscale atmospheric model-MM5(Version 3.7) and Hamburg shelf ocean model(HAMSOM),the storm surge in Bohai Sea on August 22,2008 caused by the extratropical cyclone was simulated.The forecasting fields of meteorological elements such as wind and pressure fields related to storm surge were acquired,then input them to HAMSOM and simulate storm surge in the Bohai Sea.Finally,hourly water elevation field and storm surge current field were analyzed and compared with the observational data in Tanggu station.The results indicate that when the wind direction transfers into the northwest in the western Bohai Sea,water elevation reaches 121 cm at Tanggu station.The easterly wind in the North Yellow Sea caused by long distance cyclone makes a lot of water of the North Yellow Sea flowing into the Bohai Sea,which is one of the main reasons causing the above high water elevation.This is also an important element forming storm surge,and it should be particularly concerned about storm surge forecast in future.Simulation values on extreme water elevation of storm surge and its process agree well with the observation values at Tanggu station.This particular storm surge is simulated by the numerical prediction model very well.It is difficult to judge for forecaster relying on the subjective experience if storm surge is generated in the case of offshore wind,while numerical prediction model can make up the lack of subjective analysis.