This investigation aims to study the correlation of the solar background with atmosphere. We used high resolution observations of the NaDl spectral line. In fact the large span in formation heights of this spectral line allowed us to infer the signal from photosphere to chromosphere. We analyzed the data by applying the SIR code (Stokes Inversion based on response functions). It is an inversion method of the RTE (Radiative transfer equation) that provides physical information on the region where the spectral lines are sensitive to changes in thermal and dynamical parameters of the atmosphere. The survey has been divided in two different steps: 1) identification of a model of the atmosphere that reproduce our observations; 2) determination of the degree of correlation of convective motions with the solar atmosphere. Here we present the results of the first step: we identified in the model presented by Vernazza the best model that matches our observations.