Modeling of the complex refractive index and reflectivity of flat surface water over the Persian Gulf at C-band

Abstract

For the microwave region of the electromagnetic spectrum, unlike visible light, the imaginary part of the refractive index can be significant, in which case it cannot be neglected. A well-known empirical model is not available for the direct calculation of the complex refractive index of seawater at the microwave region. However, based on the relationship between the refractive index and the permittivity, and by using the models provided for the seawater permittivity at the microwave frequencies the refractive index can be calculated. In this work, complex refractive index and normal reflectivity of Persian Gulf water at the C-band (5 GHz) have been calculated by using electromagnetic equations. The complex permittivity required for computing these parameters has been calculated from the Ellison's empirical model with measured input data. Calculations showed that the annual mean of basin-averaged of real and imaginary parts of the refractive index is 6.074 and 0.415, respectively. The relative spatial and temporal variability of the imaginary part of the refractive index is considerably stronger than its real counterpart. In all seasons, the reflection coefficient at the nadir in the western half of the Gulf is slightly higher than the eastern half and it has a minimum value of 0.5230 over the southeast waters in the summer and a maximum value of 0.5250 over the northwest waters of the Gulf Persian in winter.