Sodar Observation of the ABL Structure and Waves over the Black Sea Offshore Site

Abstract

Sodar investigations of the breeze circulation and vertical structure of the atmospheric boundary layer (ABL) were carried out in the coastal zone of the Black Sea for ten days in June 2015. The measurements were preformed at a stationary oceanographic platform located 450 m from the southern coast of the Crimean Peninsula. Complex measurements of the ABL vertical structure were performed using the three-axis Doppler minisodar Latan-3m. Auxiliary measurements were provided by a temperature profiler and two automatic weather stations. During the campaign, the weather was mostly fair with a pronounced daily cycle. Characteristic features of breeze circulation in the studied area, primarily determined by the adjacent mountains, were revealed. Wave structures with amplitudes of up to 100 m were regularly observed by sodar over the sea surface. Various forms of Kelvin–Helmholtz billows, observed at the interface between the sea breeze and the return flow aloft, are described.

Turbulence, Low-Level Jets, and Waves in the Tyrrhenian Coastal Zone as Shown by Sodar

“…The angle of the braid slopes seems to be connected with the height dependence of the mean flow speed in the wavy layer. As shown in [43,51,52], the vorticity of the wind disturbance in KHBs may be either clockwise or counterclockwise, depending on the mean wind profile. If the wind speed increases with height, then the upper part of the braid structure appears over the sodar first and, on the echogram, the tilt will be shown as directed from the point on the top left side to the bottom right.…”

“…A clear example of the second type of KHB was observed at the SMART site in an LLJ with core height of 100 m, but with a strong negative gradient of approximately −0.03 s −1 above the core, up to 400 m. The echogram and wind profile for this case are shown in Figure 32. Previous observations have mostly shown the first case or the second one (see, e.g., [51,52]), but the two KHB types have never been presented simultaneously. The question of KHB location (either in the bottom or upper part of a LLJ) is part of the general unsolved problem related to the conditions needed for the formation of KH instability in the atmosphere [58,61].…”

“…Muschinski [47] considered the possibility of the existence of Kelvin-Helmholtz billows (KHB) in LLJs, based on episodic examples of radar observations [48][49][50]; he assumed and schematically showed a possible pattern of wave braid-like structures, both below and above the LLJ core, having opposite slopes. Some experimental examples of KHBs with different slopes attributed to LLJs and different wind speed shears have been shown in [51][52][53] from sodar observations. LLJs also occur in coastal zones [3], as a component of the sea/land breeze circulation.…”

Wind Speed Profile Statistics from Acoustic Soundings at a Black Sea Coastal Site

“…In summary, it can be noted that in the literature, there are many short-term studies dedicated to the coastal boundary layer using acoustic remote sounding in different places around the world for short periods [25][26][27][28][29][30][31] and they have proved the great capabilities of the sodar measurements for the study the wind structure of the PBL. The novelty and the contribution to science of this paper consist in the statistical analyzes of sodar long-term wind speed data, which brings new information for the vertical structure of the atmosphere in coastal regions, and particularly for the Bulgarian Black Sea coast.…”

Study of the Vertical Structure of the Coastal Boundary Layer Integrating Surface Measurements and Ground-Based Remote Sensing

“…Therefore, beside point measurements at a fixed height above the ground measuring mean and turbulent of atmospheric parameters such as wind speed, U and scalars such as temperature T, humidity Q and turbulent fluxes, there is the need to investigate the development of their vertical structure. Light Detection and Ranging (LiDAR) and Sonic Detection and Ranging (SODAR) technologies have been widely used to study the vertical structure of the atmospheric boundary layer, both inland and offshore [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]: sound waves are scattered by the thermal structure of the atmosphere and light waves are scattered at small particles (Mie scattering) or at air molecules (Rayleigh scattering). Doppler LIDARs (or wind LiDAR) are now increasingly used operationally to estimate mean wind speed [ 11 ].…”