Raypath deviation under stable and unstable conditions

Dion, Denis; Seiffer, Dirk; Stein, Karin; Forand, Luc; Potvin, Guy

doi:10.1117/12.637615

Cited by 7 publications

(10 citation statements)

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“…The height of the FWG air temperature sensor was about the same. TNO buoy measurements were always systematically smaller than FWG temperature by more than 0.5 degree C. Interestingly, based on their observations of scintillation across the bay, Dion et al [2] had suggested that the actual air temperature across the bay should likely be about 0.8 degree C greater than reported by the TNO buoy. Measurements for 27 March are shown in Fig.…”

Section: Meteorological Conditionsmentioning

confidence: 98%

Measurements of transmission in the visible and the IR in the Baltic coastal environment

Dion¹,

Gardenal²,

Jong

et al. 2007

SPIE Proceedings

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A multinational campaign was organized by the NATO SET56 Group to assess transmission in coastal environments: the VAlidation Measurements of Propagation in IR and RAdar (VAMPIRA) experiment. VAMPIRA was conducted in the Baltic Sea, near Surendorf, Germany, from 27 March to 4 April 2004. During VAMPIRA, transmission was measured in the IR and the visible using a diversity of techniques. Transmissometers were installed across Eckernförde Bay, while aerosol measurements were made on the pier using Particle Measurement Systems (PMS), and visibilitymeters were deployed onshore and on a boat. Furthermore, VAMPIRA included point-target tracking experiments using blackbodies mounted on a boat. Some VAMPIRA measurements have already been presented at various symposiums. The purpose of this paper is to compare VAMPIRA transmission measurements and make comparisons with transmission estimates that can be deduced from the blackbody tracking sessions.

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Section: Meteorological Conditionsmentioning

confidence: 98%

Measurements of transmission in the visible and the IR in the Baltic coastal environment

Dion¹,

Gardenal²,

Jong

et al. 2007

SPIE Proceedings

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“…Of course in many locations, such as remote marine regions, even sparse profile datasets may not be available. In such situations, it is common to employ the Monin-Obukhov similarity theory (Monin and Obukhov 1954) to estimate the vertical profile of refractivity (MO approach) based on a single near-surface measurement, e.g., an ocean buoy (Dion et al 2001;Doss-Hammel et al 2002;Stein et al 2003;Kunz et al 2004;Dion et al 2005). Neither the HH approach nor the MO approach considers heterogeneous refractivity induced by the mesoscale atmospheric structures.…”

Section: Introductionmentioning

confidence: 98%

Influence of heterogeneous refractivity on optical wave propagation in coastal environments

Nunalee

Basu

et al. 2015

Meteorol Atmos Phys

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Spatial variations of refractivity significantly dictate the characteristics of optical wave propagation through the atmosphere. Consequently, the ability to simulate such propagation is highly dependent upon the accurate characterization of refractivity along the propagation path. Unfortunately, the scarcity of high spatiotemporal resolution observational data has forced many past studies of optical wave propagation to assume horizontally homogeneous (HH) atmospheric conditions. However, the (adverse) impact of such an assumption has not been quantified in the literature. In this paper, we attempt to fill this void by utilizing a mesoscale modelingbased approach to explicitly simulate atmospheric refraction. We then compare the differences of the HH refractivity fields to the mesoscale model-derived refractivity fields by means of a realistic atmospheric event and through ray tracing simulations. In this study, we model a coastal low-level jet, a common coastal atmospheric phenomenon which is associated with heterogeneous thermal and refractivity fields. Observational data from a radiosonde and a radar wind profiler near the northeastern region of the United States are used for model validation. The observed characteristics of low-level jet (e.g., evolution, intensity, location) and associated temperature inversion are found to be reasonably well captured by the mesoscale model. The simulated nighttime refractivity gradient field manifests significant spatial heterogeneity; over land, the refractivity gradient is much stronger and amplified near the ground, whereas it becomes much weaker over the ocean. We quantify the effect of this heterogeneity on optical ray trajectories by simulating a suite of rays and documenting the variability of their altitudes at certain propagation ranges. It is found that the altitude of optical rays may vary tens of meters during a diurnal cycle, and at nighttime the rays may bend downward by more than 150 m at a range of 100 km. We run additional ray tracing simulations using refractivity profiles from a single location and assuming HH refractivity along the propagation path. It is observed that the HH approach yields instantaneous ray bending magnitudes up to 30 % less than the ray bending based on the refractivity simulated by the mesoscale model. At the same time, it is found that the mesoscale model-based refractivity fields may have uncertainty introduced by different factors associated with the model configuration. Of these factors, turbulence parameterization is explored in-depth and found to be responsible for more uncertainty than spatial grid resolution. To be more specific, different turbulence parameterizations are found to produce significantly varying temperature inversion parameters (e.g., height, magnitude), which are critical factors influencing ray trajectories. Collectively, these results highlight the potential advantages and disadvantages of utilizing a mesoscale model to simulate refractivity in coastal areas as opposed to assuming HH refractivity.

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“…Under similar data-sparse situations, the atmospheric optics community commonly invokes the assumption of horizontal homogeneity. [8][9][10][11][12] The shortcomings of such an unphysical assumption were clearly illustrated by van Eijk and Kunz. 13 In this study, we make use of satellite-based data in tandem with in-situ measurements to avoid the assumption of homogeneity.…”

Section: Analysis Of Observational Datamentioning

confidence: 99%

“…8,9 Positive (negative) values of ASTD are associated with super-refractive (subrefractive) conditions. Unfortunately, due to the low density of meteorological stations on Lake Michigan and along its shorelines, an accurate estimation of the ASTD values is not feasible for the propagation path between Grand Haven and Milwaukee.…”

Section: Analysis Of Observational Datamentioning

confidence: 99%

Simulating an extreme over-the-horizon optical propagation event over Lake Michigan using a coupled mesoscale modeling and ray tracing framework

Basu

2017

Opt. Eng

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Simulating an extreme over-thehorizon optical propagation event over Lake Michigan using a coupled mesoscale modeling and ray tracing framework Sukanta Basu Sukanta Basu, "Simulating an extreme over-the-horizon optical propagation event over Lake Michigan using a coupled mesoscale modeling and ray tracing framework," Opt. Eng. 56 (7) Abstract. Accurate simulation and forecasting of over-the-horizon propagation events are essential for various civilian and defense applications. We demonstrate the prowess of a newly proposed coupled mesoscale modeling and ray tracing framework in reproducing such an event. Wherever possible, routinely measured meteorological data from various platforms (e.g., radar and satellite) are utilized to corroborate the simulated results.

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Raypath deviation under stable and unstable conditions

Cited by 7 publications

References 0 publications

Measurements of transmission in the visible and the IR in the Baltic coastal environment

Measurements of transmission in the visible and the IR in the Baltic coastal environment

Influence of heterogeneous refractivity on optical wave propagation in coastal environments

Simulating an extreme over-the-horizon optical propagation event over Lake Michigan using a coupled mesoscale modeling and ray tracing framework

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