Refractive Index Spectral Transfer in Inhomogeneous Turbulence in Atmospheric/Oceanic Surface Layer
Sukaran R. Patel, Univ. Federal da Paraíba, Campina Grande, Brazil
Very recently the optical scintillation has been used to remotely sense many environmental parameters, such as wind components across the propagation path, rain rates and drop size distributions and the refractive index spectrum of turbulence. Using optical scintillation measurements of the inner scale and the refractive index turbulence structure, one may obtain complete micrometeorological characteristics of the surface layer (Hill 1992). Also, the refractive index spectrum in the dissipation range is important to atmospheric optical propagation studies of both weak and very strong scintillation (Gerald and Hill, 1985). The Monin-Obukhov similarity theory is one of the most powerful tools in describing the physical properties of the atmospheroc/oceanic boundary layer. Similarity relationship, apply not only to the mean profiles of the meteorological parmeters, but also to the statistical quantities and spectral behavior of turbulence. The Monin-Obukhov similarity empirical functions are now used routinely in many practical applications (Hill 1989). Recently, a number of applications of this theory for refractive index spectrum have been reported by Hill (1989), Andreas (1987, 1988, 1989, 1990) among others. Further, there are several studies of similarity principles for horizontal homogeneous boundary layers, but very few for horizontally inhomogeneous surfaces because of their obvious difficulties. To avoid these problems most field experments have been performed in carefully chosen homogeneous conditions. But in fact the atmosphere-land-sea interface occurs in inhomogeneous surfaces. These motivate the study of various aspects of the spectral transfer of refractivity in inhomogeneous turbulence in atmospheric/oceanic boundary layer, as this is one of the several processes occuring in turbulent motion. In this study, the two-point spectrum equation for refractivity is constructed, neglecting the pressure fluctuations and the second order terms. The terms associated with both turbulence self-interaction (Batchelor 1953) and the mean gradients (Deissler 1981) in the two-point spectral equation for homogeneous turbulence can be interpreted as transfer terms. However, a similar interpretation does not seem obvious for inhomogeneous turbulence, because the condition of homogeneity is generally used in making the interpretation (Deissler 1981). Very recently, Patel (2000) using the method of Deissler (1981), has shown that certain terms in the two-point spectral equation for velocity-humidity correlation can be interpreted as spectral transfer terms, even for general inhomogeneous turbulence. In this study the discussion has been extended for the case of spectral transfer equation for refractive index. It is hoped that this study will help better understanding the modeling of the turbulent fluxes in the atmospheric/oceanic surface layer.
Poster Session 1, Environmental Applications
Monday, 15 October 2001, 9:45 AM-11:15 AM
Previous paper Next paper
Browse or search entire meeting
AMS Home Page