Detection of sensible heat flux in atmospheric turbulence by laser speckle imaging based on a cooperative target

Abstract

Sensible heat flux (H) is an important physical quantity to characterize the turbulent energy transport in the near-surface atmosphere, which is benefit for understanding the spread and diffusion of urban atmospheric pollutants and weather changes. Referring to the principle of the large aperture scintillometer (LAS) to obtain H, we propose a method for detecting H by using laser speckle imaging (LSI) system based on a cooperative target. The experiment system used 3M microcrystalline reflective film to effectively reduce the requirement of laser power. Besides, it could overcome the limitation of the complex terrain of the test field, such as islands and hills where the transportation and electricity supply are not convenient. The refractive index structure parameter 2 Cn , which is required to calculate the H, inversion from image scintillation method and centroid drift method are compared to the 2 Cn inversion by coherence length meter. The comparison results show that 2 Cn obtained by the image scintillation method are not reasonable, while the results obtained by the centroid drift method are in good agreement with the coherence length meter, especially under the circumstances of laser beam near collimation.