An effective genetic algorithm to VDA with discontinuous “on-off” switches  

作　　者：ZHENG Qin SHA JianXin FANG ChangLuan 

机构地区：[1]Institute of Science,PLA University of Science and Technology,Nanjing 211101,China [2]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG)Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China [3]Oceanic Hydrometeorological Center of the South Sea Navy Fleet,Zhanjiang 524001,China

出　　处：《Science China Earth Sciences》2012年第8期1345-1357,共13页中国科学（地球科学英文版）

基　　金：supported by National Natural Science Foundation of China (Grant Nos.40975063 and 40830955)

摘　　要：With more and more improvements of atmosphere or ocean models,a growing number of physical processes in the form of parameterization are incorporated into the models,which,on the one hand,makes the models capable of describing the at-mospheric or oceanic movement more precisely,and on the other hand,introduces non-smoothness in the form of "on-off" switches into the models."On-off" switches enhance the nonlinearity of the models and finally result in the loss of the effec-tiveness of variational data assimilation(VDA) based on the conventional adjoint method(ADJ).This study,in virtue of the optimization ability of a genetic algorithm(GA) for non-smooth problems,presents a new GA(referred to as GA NEW) to solve the problems of the VDA with discontinuous "on-off" processes.In the GA-NEW,adaptive selection and mutation oper-ators,blend crossover operator,and elitist strategy are combined in application.In order to verify the effectiveness and feasi-bility of the GA NEW in VDA,an idealized model of partial differential equation with discontinuous "on-off" switches in the forcing term is adopted as the governing equation.By comparison with the ADJ,it is shown that the GA NEW in VDA is more effective and can yield better assimilation retrievals.In addition,VDA experiments demonstrate that the performance of a GA is greatly related to the configuration of genetic operators(selection,crossover and mutation operators) and much better results may be attained with more proper genetic operations.Furthermore,the robustness of the GA NEW to observational noise,model errors and observation density is investigated,and the results show that the GA NEW has stronger robustness than the ADJ with respect to all the three observation noises,model errors,and sparse observation.With more and more improvements of atmosphere or ocean models, a growing number of physical processes in the form of parameterization are incorporated into the models, which, on the one hand, makes the models capable of describing the at- mospheric or oceanic movement more precisely, and on the other hand, introduces non-smoothness in the form of ＂on-off＂ switches into the models. ＂On-off,＇ switches enhance the nonlinearity of the models and finally result in the loss of the effec- tiveness of variational data assimilation （VDA） based on the conventional adjoint method （ADJ）. This study, in virtue of the optimization ability of a genetic algorithm （GA） for non-smooth problems, presents a new GA （referred to as GA NEW） to solve the problems of the VDA with discontinuous ＂on-off＂ processes. In the GA-NEW, adaptive selection and mutation oper- ators, blend crossover operator, and elitist strategy are combined in application. In order to verify the effectiveness and feasi- bility of the GA NEW in VDA, an idealized model of partial differential equation with discontinuous ＂on-off＂ switches in the forcing term is adopted as the governing equation. By comparison with the ADJ, it is shown that the GA NEW in VDA is more effective and can yield better assimilation retrievals. In addition, VDA experiments demonstrate that the performance of a GA is greatly related to the configuration of genetic operators （selection, crossover and mutation operators） and much better results may be attained with more proper genetic operations. Furthermore, the robustness of the GA NEW to observational noise, model errors and observation density is investigated, and the results show that the GA NEW has stronger robustness than the ADJ with respect to all the three observation noises, model errors, and sparse observation.

关 键 词：variational data assimilation ＂on-off＂ switches genetic algorithm 

分 类 号：O242.23[理学—计算数学] TP273[理学—数学]