Coastal Boundary-Layer Characteristic During Night Time Using a Long-Term Acoustic Remote Sensing Data

The study of the Planetary Boundary Layer vertical structure in coastal areas is of particular importance due to the fact that a large number of urban areas and their industrial activities are located on the shores of the seas, oceans or large lakes. Based on long-term (August 2008–October 2016) sodar measurements at a Bulgarian Black Sea coastal site, the mean characteristics of the two main types of nocturnal air flows (marine and land air masses) are obtained. Typical parameters for the investigated region, such as the heights of the marine, the internal and planetary boundary layers, as well as wind and turbulence vertical structure details are revealed exploring this high spatial (10 m) and temporal (10 min) resolution data. The observation site is near the town of Ahtopol in Southeast Bulgaria. The analyses are based on averaging of the measured profiles of 12 output sodar parameters and calculated Buoyancy Production mean profiles. The seasonal variability of all characteristics is explored. The nocturnal land air masses are found to be with neutral and slightly stable stratification, Planetary Boundary-Layer height of 410–430 m and corresponding Surface-Layer height of 50–80 m. The nocturnal marine air masses are found to be with neutral and slightly unstable stratification, Internal Boundary-Layer height of about 40–50 m and a nocturnal marine Planetary Boundary-Layer height of about 300 m. The study contributes to disclosure and understanding the coastal nocturnal wind and turbulence regime in a region with modest observation networks. The obtained results can be also used for evaluation of the various theoretical, mesoscale and air quality models performance.