Research On Temperature And Current Distribution Inverting Based On High Frequency Acoustic Tomography In Estuaries And Basins

Estuary as an important platform for the land and ocean flows,teeming with dense human activities,constitutes a frontier zone for ocean research.The environmental problems in estuarine region are hotspots on estuary research,including a sharp decrease of the sediment flux,the increase of land-sourced pollutants,wetland encroachment,and the abnormality of water temperature distribution.To address these branches of estuary research requires accurate real-time monitor on temperature distribution,current distribution and water runoff flux.Distributions of temperature and current in the estuarine region present obvious spatial variations introduced by the dual effect of runoff and tide.To monitor the temperature and current in real time needs endless efforts and this study is devoted to introducing an inversion system which can be applied to monitoring the temperature and current distributions in estuaries and watersheds.This study is based on acoustic tomography.Sounds can be affected by the thermodynamics and dynamics processes like temperature and flow fields in the medium,which can be used to collect information through sound propagation.In theory,the difference of acoustic signals in transmitting and receiving terminals within a certain range can be used to reconstruct environmental characteristics of the medium.Though acoustic tomography has been successfully used in offshore and estuarine areas,efforts are still needed to overcome shortcomings in the practical application,such as high cost and long measurement time.Based on the existing coastal acoustic tomography theory,models and devices,we put forward a new,low-cost and efficient method to reconstruct temperature and current distributions,as a supplement to coastal acoustic tomography application.Systematic simulation and calibration under various environments verified the reliability of the system.In addition,field experiments were conducted for a continuous monitoring of 5 months in Beixi reservoir and Jiulong River,Zhangzhou city.Results show that the system can maintain a stable work for a long time,and present a high data coverage during the whole observation period.The real-time temperature and current data are highly correlated with the results from traditional measurement devices.This system can meet the needs of temperature and current measurement in estuaries and watersheds at a low cost.