Synoptic Classification and Horizontal Homogeneity of the Refractive Index Structure Function Parameter in the Surface Layer

AbstractThis paper discusses the derivation of the refractive index structure function. It shows that the traditional formulation, which is based on the hydrostatic assumption, leads to increasing errors with height when compared with a formulation that is based on the potential temperature. The paper corrects a long-standing problem of extrapolating the traditional boundary layer approximation beyond its region of validity (i.e., to the upper troposphere and lower stratosphere). The new derivation may have applications in observational work to measure and seeing and in numerical modeling efforts. A preliminary analysis of the influence of the new formulation in numerical modeling of seeing suggests that impact on seeing will be small in general, because the largest contribution to seeing generally comes from the lower troposphere. However, an accurate profile is needed because other astroclimatic parameters, such as the isoplanatic angle, can suffer from the lack of accuracy at high altitude. This work may also have application in radar meteorology, since clear-air radar sensitivity depends on accurate estimation of .

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Simulating the Refractive Index Structure Constant $({C}_{n}^{2})$ in the Surface Layer at Antarctica with a Mesoscale Model

The Astronomical Journal ◽

10.3847/1538-3881/aa9e8f ◽

2017 ◽

Vol 155 (1) ◽

pp. 37 ◽

Cited By ~ 3

Author(s):

Chun Qing ◽

Xiaoqing Wu ◽

Xuebin Li ◽

Qiguo Tian ◽

Dong Liu ◽

...

Keyword(s):

Refractive Index ◽

Surface Layer ◽

Mesoscale Model ◽

Structure Constant ◽

Index Structure

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Diurnal cycles of the refractive index structure function coefficient

Journal of Geophysical Research Atmospheres ◽

10.1029/jc078i027p06224 ◽

1973 ◽

Vol 78 (27) ◽

pp. 6224-6232 ◽

Cited By ~ 29

Author(s):

M. L. Wesely ◽

E. C. Alcaraz

Keyword(s):

Refractive Index ◽

Structure Function ◽

Index Structure ◽

Diurnal Cycles ◽

Function Coefficient

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A new method for measuring the imaginary part of refractive index structure parameter in the urban surface layer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-21285-2014 ◽

2014 ◽

Vol 14 (15) ◽

pp. 21285-21314 ◽

Cited By ~ 1

Author(s):

R. Yuan ◽

T. Luo ◽

J. Sun ◽

Z. Zeng ◽

Y. Fu

Keyword(s):

Refractive Index ◽

Surface Layer ◽

Imaginary Part ◽

Intensity Fluctuation ◽

Index Structure ◽

Urban Surface ◽

Structure Parameter ◽

The Real ◽

Urban Surface Layer ◽

Refractive Index Structure Parameter

Abstract. Atmospheric refractive index consists of both the real and the imaginary parts. The intensity of refractive index fluctuation is usually expressed as the refractive index structure parameter, whose real part reflects the strength of the atmospheric turbulence while the imaginary part reflects the absorption in the light path. The large aperture scintillometer (LAS) is often used to measure the structure parameter of the real part of atmospheric refractive index, and the sensible and latent heat fluxes can further be obtained, while the influence of the imaginary part is ignored, or thought to be a noise. Based on the expression for the spectrum of the logarithmic light intensity fluctuation caused by the imaginary part of refractive index, new expressions for the logarithmic intensity fluctuation variance and the structure function related to the imaginary part of refractive index are derived. Then a simple expression for the imaginary part of the atmospheric refractive index structure parameter (ARISP) is obtained. It can be conveniently used to measure the imaginary part of the ARISP from LAS. Experiments of light propagation were performed in the urban surface layer and the imaginary part of the ARISP was calculated. The experimental results showed a good agreement with the presented theory. The results also suggested that, the imaginary part of ARISP shows a different variation from the real part of ARISP. For the light with the wavelength of 0.62 μm, the variation of the imaginary part of ARISP is related to both the turbulent transport process and the spatial distribution characteristics of aerosols. Based on the theoretical analysis, it can be expected that the method presented in this study can be applied to measuring the imaginary part of the ARISP caused by the trace gas, if the light wavelength is selected within the corresponding gas absorption region.

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Simultaneous observations of structure function parameter of refractive index using a high-resolution radar and the DataHawk small airborne measurement system

Annales Geophysicae ◽

10.5194/angeo-34-767-2016 ◽

2016 ◽

Vol 34 (9) ◽

pp. 767-780 ◽

Cited By ~ 6

Author(s):

Danny E. Scipión ◽

Dale A. Lawrence ◽

Marco A. Milla ◽

Ronald F. Woodman ◽

Diego A. Lume ◽

...

Keyword(s):

Refractive Index ◽

High Resolution ◽

Structure Function ◽

Lower Troposphere ◽

Unmanned Aircraft ◽

Function Parameter ◽

High Temporal Resolution ◽

Atmospheric Measurements ◽

Range Resolution

Abstract. The SOUSY (SOUnding SYstem) radar was relocated to the Jicamarca Radio Observatory (JRO) near Lima, Peru, in 2000, where the radar controller and acquisition system were upgraded with state-of-the-art parts to take full advantage of its potential for high-resolution atmospheric sounding. Due to its broad bandwidth (4 MHz), it is able to characterize clear-air backscattering with high range resolution (37.5 m). A campaign conducted at JRO in July 2014 aimed to characterize the lower troposphere with a high temporal resolution (8.1 Hz) using the DataHawk (DH) small unmanned aircraft system, which provides in situ atmospheric measurements at scales as small as 1 m in the lower troposphere and can be GPS-guided to obtain measurements within the beam of the radar. This was a unique opportunity to make coincident observations by both systems and to directly compare their in situ and remotely sensed parameters. Because SOUSY only points vertically, it is only possible to retrieve vertical radar profiles caused by changes in the refractive index within the resolution volume. Turbulent variations due to scattering are described by the structure function parameter of refractive index Cn2. Profiles of Cn2 from the DH are obtained by combining pressure, temperature, and relative humidity measurements along the helical trajectory and integrated at the same scale as the radar range resolution. Excellent agreement is observed between the Cn2 estimates obtained from the DH and SOUSY in the overlapping measurement regime from 1200 m up to 4200 m above sea level, and this correspondence provides the first accurate calibration of the SOUSY radar for measuring Cn2.

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