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.

Quantification of surface layer turbulence using sensible heat values from energy balance versus aerodynamic methods.

Surface layer optical turbulence values in the form of the refractive index structure function 2 are often calculated from surface layer temperature, moisture, and wind characteristics and compared to measurements from sonic anemometers, differential temperature sensors, and imaging systems. A key derived component needed in the surface layer turbulence calculations is the sensible heat value. Typically, the sensible heat is calculated using the bulk aerodynamic method that assumes a certain surface roughness and a friction velocity that approximates the turbulence drag on temperature and moisture mixing from the change in the average surface layer vertical wind velocity.

Investigating turbulence distribution in the lower atmosphere using time-lapse imagery from a camera bank.

The atmosphere's surface layer (first 50-100 m above the ground) is extremely dynamic and is influenced by surface radiative properties, roughness, and atmospheric stability. Understanding the distribution of turbulence in the surface layer is critical to many applications, such as directed energy and free space optical communications. Several measurement campaigns in the past have relied on weather balloons or sonic detection and ranging (SODAR) to measure turbulence up to the atmospheric boundary layer.

"Hidden phase" in two-wavelength adaptive optics.

Two-wavelength adaptive optics (AO), where sensing and correcting (from a beacon) are performed at one wavelength and compensation and observation (after transmission through the atmosphere) are performed at another , has historically been analyzed and practiced assuming negligible irradiance fluctuations (i.e., weak scintillation).

Implications of polarized pupil degradation due to focal shifts in dynamically ranged Rayleigh beacons.

A dynamically ranged pulsed Rayleigh beacon using sensed wavefronts across a system's pupil plane is proposed for tomographic quantification of the atmospheric turbulence strength. This method relies on relaying light from a telescope system's pupil plane to a wavefront sensor and having precise control of the light-blocking mechanisms to filter out scattered light from the unwanted scattering regions along the propagation path. To accomplish this, we tested and incorporated design features into the sensing system that we believe, to the best of our knowledge, are unique.

Polychromatic wave-optics models for image-plane speckle. 1. Well-resolved objects.

Polychromatic laser light can reduce speckle noise in wavefront-sensing and imaging applications that use direct-detection schemes. To help quantify the achievable reduction in speckle, this paper investigates the accuracy and numerical efficiency of three separate wave-optics methods. Each method simulates the active illumination of extended objects with polychromatic laser light.