Horizontal Flow Velocity Field And Temperature Field Observation Of Artificial Upwelling Areas With Coastal Acoustic Tomography

At present,the marine ecological environment has been seriously damaged.The artificial upwelling can effectively improve the marine ecological environment and play an important role in alleviating global warming and reducing marine natural disasters.However,there is still a lack of methods for long-term sequence observations in artificial upwelling regions.The existing observation methods have problems such as limited observation data and complex observation network structure,and it is impossible to realize long-term observation in a small-scale sea area.Coastal acoustic tomography can use fewer instruments to perform large-scale,long-term simultaneous observations,and is not limited by the near-shore busy shipping activities and fishing activities.In this paper,a method of coastal acoustic tomography is proposed to observe the artificial upwelling area in a long time series,which can effectively remedy the shortcomings of the long-term observation of the flow velocity and temperature fields in the artificial upwelling area.This method will play an important role in the long-term observation of the flow velocity and temperature fields in the artificial upwelling area and other small areas.This paper has carried out theoretical analysis,numerical simulation and experimental observation.Firstly,this paper introduces the acoustic propagation mode in the artificial upwelling ocean environment.The Bellhop ocean acoustic propagation model is used to simulate the sound ray and acoustic signal propagation losses in the artificial upwelling region.Then the theoretical method of observation of horizontal flow velocity field and temperature field using the coastal acoustic tomography method in the artificial upwelling zone is studied.Then the numerical simulation of the artificial upwelling temperature field is carried out.The numerical simulation of the artificial upwelling temperature field is carried out.The influence of the number of different stations and the location distribution on the inversion temperature field is discussed.On the basis of theoretical research,a 28-day artificial upwelling observation experiment was carried out in the anechoic tank of Zhejiang University's Shuisheng Museum.The influence of station number and position distribution on the inversion accuracy of horizontal flow velocity field and temperature field is analyzed.Finally,in order to verify the feasibility of the actual sea area acoustic tomography observation,this paper used four coastal acoustic tomography systems in the waters near the Zhairuoshan island of Zhoushan to carry out small-range flow field experiments.The numerical simulation results of horizontal temperature field show that it is feasible to select rectangular layout of observation stations in artificial upwelling area,and the inversion accuracy of temperature field is the highest in the eight stations.The artificial upwelling was successfully observed in the pool experiment,indicating that it is feasible to observe the horizontal flow velocity field and temperature field of the artificial upwelling areas by the coastal acoustic tomography method,and summarize the characteristics of the horizontal flow velocity field and temperature field of the artificial upwelling areas.The flow velocity field in the 300-meter range was successfully observed in the Zhairuoshan Island,and the results obtained from the inversion of the flow velocity field by coastal acoustic tomography are basically consistent with the ADCP observation data.It shows that it is feasible to use the coastal acoustic tomography method to observe the small-scale flow velocity field,and the artificial upwelling areas is also a small-scale sea areas,so this will provide an important data reference for the observation of small-scale sea areas such as the artificial upwelling areas.