Optik 153 (2018) 86–94 Contents lists available at ScienceDirect Optik journal homepage: www.elsevier.de/ijleo Original research article A new atmospheric spectral model for the marine environment F. Khannous, A. Belafhal ∗ Department of Physics, Faculty of Sciences, Chouaïb Doukkali University, P. B 20, 24000 El Jadida, Morocco a r t i c l e i n f o Article history: Received 16 June 2017 Accepted 29 September 2017 Keywords: Maritime atmospheric turbulence Maritime power spectrum Scintillation index a b s t r a c t In this paper, we derive a new expression of marine atmospheric spectrum, by fitting a numerical spectrum and based on the refractive index power spectral model for the marine environment existing in the literature. Also, under weak optical turbulence, the analytic expressions of scintillation index are determined for plane and spherical waves in mar- itime atmospheric environment by using our new maritime atmospheric spectrum model. A comparison between our results and the existing scintillation theory for the maritime and terrestrial atmospheric media is also established. The obtained results show that the new spectrum is adequate for describing the marine atmosphere in weak optical turbulence for small values of the inner scale of turbulence. © 2017 Elsevier GmbH. All rights reserved. 1. Introduction The marine atmosphere, which represents the atmosphere above the sea or ocean, is characterized by the increase in humidity, temperature fluctuations and changes in wind direction. Because of the different environments, maritime atmo- spheric turbulence differs from terrestrial atmospheric turbulence. In the literature, some models have been investigated and developed to describe the marine atmospheric spectrum. This medium has different effects on the propagation of opti- cal waves through it compared with the atmosphere above land. Recently, Grayshan et al. [1] have developed a new power spectrum to describe the behavior of turbulence in a turbulent maritime environment; since then, the influence of marine environment on laser beam propagation has been extensively studied theoretically and experimentally. It is based on the downhill simplex algorithm to fit a numerical spectrum and derive analytical expression for the irradiance scintillation index of a plane and a spherical waves in marine environment. In the literature, this spectrum has been widely used in some studies to determine the various effects of marine atmosphere media. Cheng et al. [2] have used the maritime atmospheric spectrum to evaluate scintillation and aperture averaging for Gaussian beams through non-Kolmogorov maritime atmospheric turbu- lence channels. Baykal [3] have developed scintillation of higher-order laser beam in weakly turbulent marine atmospheric medium by the use of the developed spectrum. Also, in recent years, the effect of maritime atmospheric turbulence on the propagation of Li’s flattened Gaussian and hollow Gaussian beams have investigated by Khannous et al. [4–6]. The purpose of this paper is to present an improvement of the atmospheric spectral model for the marine environment. An analytical marine atmospheric spectrum is formulated to fit a numerical spectrum by the use of the expression of the spectrum proposed in the literature. The rest of this paper is organized as follows: In Section 2, we present and derived theoretically the analytical expression of our new modified spectrum. In Section 3, we formulate and evaluate the scintillation ∗ Corresponding author. E-mail address: belafhal@gmail.com (A. Belafhal). https://doi.org/10.1016/j.ijleo.2017.09.119 0030-4026/© 2017 Elsevier GmbH. All rights reserved.