Comparative analysis of 2 estimation methods for sonic anemometer data.

Wind speed and sonic temperature measured with ultrasonic anemometers are often utilized to estimate the refractive index structure parameter 2, a vital parameter for optical propagation. In this work, we compare four methods to estimate 2 from 2, using the same temporal sonic temperature data streams for two separated sonic anemometers on a homogenous path. Values of 2 obtained with these four methods using field trial data are compared to those from a commercial scintillometer and from the differential image motion method using a grid of light sources positioned at the end of a common path.

Relationship between turbulent image variance and average image gradient.

Optical turbulence can cause substantial distortions in imaging over long horizontal paths. For Lambertian objects, these distortions are only seen where there is a gradient in the object's radiance. It is possible to establish a relationship between the intensity variance of a turbulent image and the average image's gradient squared.

General Rytov approximation.

We examine how the Rytov approximation describing log-amplitude and phase fluctuations of a wave propagating through weak uniform turbulence can be generalized to the case of turbulence with a large-scale nonuniform component. We show how the large-scale refractive index field creates Fermat rays using the path integral formulation for paraxial propagation. We then show how the second-order derivatives of the Fermat ray action affect the Rytov approximation, and we discuss how a numerical algorithm would model the general Rytov approximation.

Hydrodynamics of the turbulent point-spread function.

We derive hydrodynamic equations for the point-spread function of an imaging system looking through atmospheric turbulence at an incoherent object. These are derived from the hydrodynamics of the index of refraction of the air. We use the path integral representation of the paraxial approximation for wave propagation through turbulence.

Some theoretical aspects of the turbulent point-spread function.

In a previous work [J. Opt. Soc.

Some space-time statistics of the turbulent point-spread function.

We consider the point-spread function (PSF) of an imaging system looking through weak optical turbulence along a horizontal path through the atmospheric surface layer. From this PSF we derive a scalar total irradiance field and a center-of-mass vector field. Theoretical values are found for the space-time autocorrelation and cross-correlation functions for these fields, which are then compared with the observed correlation functions obtained from data taken at the Validation Measurements on Propagation in the Infrared and Radar (VAMPIRA) measurement trial.

Detailed analytical approach to the Gaussian surface bidirectional reflectance distribution function specular component applied to the sea surface.

A statistical sea surface specular BRDF (bidirectional reflectance distribution function) model is developed that includes mutual shadowing by waves, wave facet hiding, and projection weighting. The integral form of the model is reduced to an analytical form by making minor and justifiable approximations. The new form of the BRDF thus allows one to compute sea reflected radiance more than 100 times faster than the traditional numerical solutions.