High-precision Approximation Modeling And Calculation Of Chlorophyll ? Parameters In Artificial Upwelling

Artificial upwelling can enhance the primary productivity in the sea area by carrying rich nutrients in deep water to the surface of the sea and provide an important support for fishery production.Chlorophyll-a is one of the impor-tant indexes for water-quality assessment.Monitoring water-quality parameters reasonably and predicting chlorophyll-a concentration accurately can effectively prevent the artificial upwelling from being brought the eutrophication,which can maximize the benefits artificial upwelling brings.Based on the artificial upwelling of wave energy,two methods,discontinu-ous piecewise fitting(also called as regression)and continuous piecewise fitting,were established in this paper.Based on the chlorophyll-a concentration as the dependent variable,nutrient concentration,depth,temperature,salinity as independent variables,linear and non-linear(quadratic)piecewise model were established to explore the relationship between variables,and compared with the traditional overall fitting model.In this paper,the fast algorithm for calculating the discontinuous piecewise quadratic fitting and the time complexity of the al-gorithm are given,and the upper bound of mean square error of the algorithm is proved.Considering the continuity of the water parameters under the physical meaning,we further propose the model of continuous piecewise fitting by adding the equal boundary conditions on the basis of minimizing the error function to construct a new optimization function,and propose the parametric equation.In the process of solving the fitting parameters,there is a problem that the condi-tional number of the coefficient matrix is too large.Therefore,a regularization iterative method is used to solve the problem in this paper.Finally,by dividing the sample of laboratory monitoring data into training samples and prediction samples according to a certain proportion,this paper conducts model training,prediction and evaluation.The results show that there is a strong correlation between chlorophyll-a concentration and salinity,tem-perature,dissolved oxygen content and pH.Compared with the overall fitting,the goodness-of-fit of the piecewise model has been significantly improved;the continuous piecewise quadratic regression has the best generalization ability.