Internal boundary layer characteristics at the southern Bulgarian Black Sea coast

Abstract

Abstract. The marine Atmospheric Boundary Layer (ABL) over the southern Bulgarian Black Sea coast is studied based on remote sensing measurements with a monostatic Doppler sodar system located at about 400 m inland. Long-term profile data (August 2008–October 2016) with high spatial (10 m) and temporal (20 min running averages at every 10 min) resolution was analysed to reveal the complex vertical structure of the coastal ABL at marine airflow. The processes of air masses transformation due to the sharp change in physical characteristics of the underlying surface lead to Internal Boundary Layer (IBL) formation. Its spatial scales as a sublayer of the coastal ABL depend on the distance from the shore. In the absence of temperature and humidity profile measurements, the turbulent profiles of marine air masses of different fetch over land (400 to 2500 m) were used to examine the characteristics of the IBL. Different fetch or distance passed by the marine airflow before reaching the sodar is considered selecting intervals of wind directions. IBL heights between 60 and 150 m depending on the fetch are obtained.