Preliminary analysis of the vertical wind profiles measured using Acoustic Wind Profiler Sodar MFAS installed at the Split airport (Croatia)

The Scintec Acoustic Wind Profiler Sodar MFAS was installed at Split Airport (on the Adriatic coast, Croatia) in December 2022. However, due to power consumption issues, the instrument was not fully operational until June 2023, when it was connected to the regular power grid. Five months of measurements, from June to October 2023 were analysed: during this period, the time step of the measurements was set to 20 minutes, resulting in 20-minute averages of horizontal and vertical wind at heights ranging from 30 m to a maximum of 400 m, with a 10-m vertical step. The top height of the measurements was strongly dependent on the background atmospheric conditions.

From June to October 2023, several characteristic winds were observed: (1) sea and land breezes; (2) sirocco (Cro. "jugo") - strong, steady southeast wind bringing moisture; and (3) bora (Cro. "bura") - cold, strong, and gusty northeast wind. Since the measurements were made during the warmer part of the year, the sea and land breezes were the predominant winds, which were then further analysed. The mean daily vertical profile of the sea and land breezes was estimated: the breezes rotated clockwise during the day, starting as weak easterly to southeasterly winds with a speed of 2-3 m/s in the early morning hours, turning to weak southerly winds around noon, and then to faster southwesterly winds with a speed of ~5 m/s around 1 pm local time. The sea breezes reached their maximum speed around 4 pm local time and maintained their southwesterly direction. After 4 pm local time, the breezes generally began to weaken and change direction, first to westerly and then to northwesterly winds, which ceased around 8 pm local time. Easterly to northeasterly land breezes typically started couple of hours later, reaching up to ~5 m/s. The vertical structure of the sea and land breezes was further analysed: Preliminary analyses indicate that during the daytime hours, the horizontal winds were fairly uniform in the first 400 m and maintained their direction, but gained some speed with height. On the other hand, a reversal of circulation was frequently observed during the nighttime hours, from weaker easterly winds in the lowest 200 m to stronger northwesterly winds at 200-400 m altitude.

The synoptic conditions favourable for the occurrence of sea and land breezes were then extracted using the ERA5 Global Reanalysis dataset.

Additional Sodar MFAS measurements will be used to analyse sirocco and bora, i.e., winds that occur more frequently during the colder part of the year.