Reflection loss from a "Pierson-Moskowitz" sea surface using the nonlocal small slope approximation

1999 ◽  
Vol 37 (1) ◽  
pp. 632-634 ◽  
Author(s):  
S.L. Broschat
Keyword(s):  
Reflection Loss ◽  
Sea Surface

scholarly journals The Vertical Distribution of Marine Macroplankton. X. Notes on the Behaviour of Sagitta in the Plymouth Area

1931 ◽  
Vol 17 (2) ◽  
pp. 391-414 ◽  
Author(s):  
F. S. Russell
Keyword(s):  
Vertical Distribution ◽  
Reflection Loss ◽  
Early Morning ◽  
Sea Surface ◽  
Light Conditions ◽  
The Vertical Distribution ◽  
Diurnal Behaviour ◽  
Transparent Water

1. The diurnal behaviour of Sagitta of different sizes is shown as a result of collections made with the 2-metre stramin ring-trawl throughout 24 hours on July 15th–16th, 1924, and on June 3rd–4th, 1926.2. The younger stages of Sagitta elegans appear to withstand higher intensities of light in the daytime than do the older stages, and they migrate first to the surface at dusk, as do those of Sagitta setosa. The older stages leave the surface first at dawn.3. Diagrams are given showing the curves of equal intensities of light beneath the sea surface throughout 24 hours as calculated from air intensities obtained in June, with a reflection loss of 15%; (a) assuming a coefficient of absorption of 0·200 at all depths, and (b) assuming a coefficient of absorption of 0·100 at all depths.4. It appears, from a comparison of the behaviour of Sagitta elegans with the calculated light conditions beneath the surface, that the older Sagitta at any rate are more sensitive to light in the early morning after the darkness of the night and can become adapted to light of higher intensities later in the day.5. Previously published observations on the behaviour of Sagitta sp. on June 17th–18th–19th, 1925, show quite a different type of behaviour from the above, possibly due to more transparent water, the Sagitta only appearing abundantly above 30 metres in the dark. They had again migrated to below 30 m. before there was any appreciable light.

The Effect of Sea State on the Polarization of Reflected Beidou B1 Signals

2020 ◽  
Vol 13 (5) ◽  
pp. 736-742
Author(s):  
Tingting Lyu ◽  
Shuang Sha ◽  
Min Zhang ◽  
Hao Zhang ◽  
Thomas A. Gulliver
Keyword(s):  
Reflection Loss ◽  
Specular Reflection ◽  
Signal To Noise Ratio ◽  
Incident Angle ◽  
Surface States ◽  
Sea Surface ◽  
Polarization Diversity ◽  
Angle Of Incidence ◽  
Circularly Polarized ◽  
Surface Conditions

Background: Oceanographic buoys generally employ satellites for positioning and data transmission. However, sea surface conditions can affect these signals. The Signal to Noise Ratio (SNR) of small observation buoys can be improved by exploiting polarization diversity. Methods: This paper discusses the effect of sea surface conditions on the polarization and reflection loss of Beidou B1 reflected signals for the purposes of exploiting polarization diversity. The Rayleigh roughness criterion is used to assess the roughness of the sea surface. The Fresnel reflection coefficients are derived to analyze the polarization and reflection loss of the Beidou B1 reflected signals with different sea surface states. Results: The results obtained show that for the Beidou B1 signals, the sea surface is considered rough for most sea surface states and incident angles. For smooth sea surfaces, the Beidou B1 reflected signals are mainly Left Hand Circularly Polarized (LHCP) waves, but Right Hand Circularly Polarized (RHCP) waves dominate when the incident angles are larger than the Brewster angle. The reflected loss is between -2 dB to -3.4 dB. In rough sea surfaces and the signals propagation is dominated by diffuse reflection. The reflection loss decreases with the incident angle and there is a fluctuation when the incident angle is around 49 degrees. The specular reflection signal has a significant amplitude when the angle of incidence is large. RHCP waves are the main component of the reflected signals, and the reflection loss is relatively small which can be employed for polarization diversity or marine remote sensing. Conclusion: polarization diversity is only useful with good sea conditions, and the corresponding gain decreases with the deterioration of the sea surface conditions.

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