Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels

An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments

Iaoos Observations of Aerosols and Clouds in the High Arctic by Autonomous Drifting Lidar Platforms

New drifting platforms have been deployed within the French project IAOOS (Ice-Atmosphere-Ocean Observing System) in the Arctic since 2014. Radiation and meteorological parameters are measured at the surface and profiles of aerosol and cloud properties are obtained with autonomous backscatter lidar systems. These platforms are indeed equipped for ocean-ice-atmosphere studies over the Arctic to better understand processes and interactions controlling sea-ice changes [1]. As stations in the Arctic are sparse, they can also be used as reference measurements for satellite observations. They are deployed in the Arctic almost every year and allow to perform regular measurements of the vertical structure and optical properties of the atmosphere in complement to satellite observations. Other data on snow, ice and ocean are simultaneously measured. Comparisons were made with CALIPSO/CALIOP observations. Measurements on the atmosphere are presented and results are discussed