Abstract: A scheme for estimating the turbulent diffusivity in the atmosphere based on an inverse problem methodology is presented. The inverse problem is formulated as a nonlinear constrained optimization problem, where the objective function is defined as the square difference between experimental and model data. In the presence of noise is necessary to use regularization operators. The Tikhonov and entropic regularization of zeroth, first and second orders are used. The direct model consists in the diffusion equation solved by a second-order finite difference method. Numerical experiments show a good performance of the proposed methodology.