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PROPAGATION OF ELECTROMAGNETIC WAVE IN ATMOSPHERIC BOUNDARY LAYER USING LARGE EDDY SIMULATION A. Dipankar and P. Sagaut

Large-eddy simulation (LES) has been successfully used by the atmospheric community to generate fine resolution fields of turbulent refractivity. These fields can be directly used for the wave propagation problem in the megahertz range but not for the waves of higher frequencies. Numerical computation of these high frequency waves require very fine grid resolution, which is beyond the capabilities of the existing supercomputers. For this reason the physicists, working in Electromagnetic (EM) wave propagation modeling, prefer to artificially generate the refractive index fluctuations using a given spectra. This makes the turbulent spectra very important for the wave propagation modeling, which needs to be modeled for spatial scales ranging from large resolvable scales to the scales in the dissipation range, beyond the LES cut-off. In the present work and to our knowledge for the first time, the results obtained from the LES of a moist convective boundary layer, are used to estimate all the key parameters defining the refractive index spectra. Propagation of EM waves in a turbulent medium is solely characterized by these parameters. These parameters are the refractive index structure function parameter C2 n, the inner scale l0 and the outer scale L0 of the turbulent field. These parameters are estimated for the waves in visible frequency range, at different altitudes. The results are then used to study the intensity variance of the scattered waves.