Research On Chlorophyll Assimilation Simulation In Taihu Lake Based On Ensemble Kalman Filter

In recent years,the problem of lake water pollution and eutrophication has become increasingly serious.Lake water pollution has seriously affected the ecology of the earth and people's living environment.It is imperative to strengthen the monitoring and treatment of lake water pollution.Numerical model simulation is an effective method for the simulation and prediction of lake water quality.It can simulate the complex lake flow state and the changes of lake water quality.However,due to the complexity of the evolution mechanism of lake hydrodynamics/water quality,the large number of simulation parameters and the difficulty in data acquisition,the numerical model simulation has large errors in long-term sequence simulation and the simulation results are inaccurate.The high frequency of field measurement data can accurately monitor the changes in water quality.Therefore,we can consider the use of data assimilation methods combined with measurement data to achieve real-time correction of model simulation results.Ensemble Kalman Filter is a sequential data assimilation method.The generate of initial perturbation field is the key step in Ensemble Kalman Filter,which has an important influence on the assimilation result.The standard Ensemble Kalman Filter uses the Monte Carlo method to generate the initial perturbation field,and the resulting error rate of the perturbation field is not high;while the error growth rate of the perturbation field generated by the Breeding of Growing Modes is better than the Monte Carlo,but it has some problem such as short-term non-increase in the error and need long time to saturation.Therefore,we can consider dynamic BGM method to generate the initial perturbation field to reduce the influence of the initial perturbation in the Ensemble Kalman Filter assimilation method.Based on this,this paper used the Ensemble Kalman Filter assimilation method,coupled with the FVCOM three-dimensional hydrodynamic model,designed adynamic BGM initial perturbation field generation method,and used Taihu Lake chlorophyll measured data and meteorological and hydrological data,to constructe the Taihu Lake chlorophyll assimilation simulation model based on the Ensemble Kalman Filter.Then,this paper used high-frequency measured data to modify model simulation results,and developed different perturbation field generation comparative study on Chlorophyll assimilation cases in Taihu Lake Based on Ensemble Kalman Filter.The main research contents and achievements of this article are as follows:(1)Research on Dynamic BGM Method to generate initial perturbation fieldFor the problem that the perturbation growth rate generated by the Monte Carlo method to generate initial perturbation field is not high and the short-term non-increase in error,long-term growth of perturbation growth rate by BGM method to generate initial perturbation field.This paper designed dynamic BGM method and detailed implementation program to generate initial perturbation field,and realized The application of dynamic BGM generation initial perturbation field in Ensemble Kalman Filter,and reduced the influence of initial perturbation to Ensemble Kalman filter assimilation simulation,improved the effect of the Ensemble Kalman Filter assimilation simulation.(2)Research on chlorophyll assimilation simulation in Taihu Lake based on Ensemble Kalman FilterBased on the measured data of chlorophyll and hydrometeorological data in Taihu Lake,this paper studied the data assimilation method of Ensemble Kalman Filter and integrated the three-dimensional hydrodynamic model of FVCOM,constructed assimilation simulation model based on Ensemble Kalman Filter,developed chlorophyll assimilation simulation method research in Taihu Lake based on Ensemble Kalman Filter,realized the use of high-frequency chlorophyll measured data to correct model operation results,and improved the accuracy of the model simulation results.By use of visualization method,the temporal and spatial distribution of chlorophyll concentration in Lake Taihu was reproduced,which provided supportive decision for the treatment of Taihu Lake water pollution.(3)Ensemble Kalman Filter assimilation simulation contrast experiment based on dynamic BGMIn order to verify the effectiveness of the dynamic BGM method designed in this paper,we use the constructed assimilation model,to carry out he Ensemble Kalman Filter assimilation simulation contrast study based on dynamic BGM.This paper designed the model simulation experiment,the standard Ensemble Kalman Filter assimilation simulation experiment,BGM Ensemble Kalman Filter assimilation simulation experiment and the dynamic BGM Ensemble Kalman Filter assimilation simulation experiment.Comparing the experimental results with the accuracy of the four experiments,it shows that the Ensemble Kalman Filter assimilation simulation based on dynamic BGM is effective,and the standard Ensemble Kalman Filter assimilation simulation,the BGM Ensemble Kalman Filter assimilation simulation and the dynamic BGM Ensemble Kalman Filter assimilation simulation are improved the accuracy of the model simulation in different extent.