Gradient calculation based ensemble variational method and its application to the inversion of the turbulent coefficient in atmospheric Ekman layer

Abstract

The accurate value of the turbulent coefficient in Ekman layer of atmosphere is quite important for the numerical weather prediction and pollutant diffusion calculation. In the paper, based on ensemble method and variational method, the ensemble variational retrieval method is proposed, and the gradient of objective function is calculated with the method. Two calculation procedures are also given based on the linear condition of forward model. The inversion numerical experiments of the turbulent coefficient using ensemble variational method and two calculation flow process are carried out, and the results show that the method has the simple and convenient characteristics, and the turbulent coefficient can be retrieved accurately by observational data.