Mirko Orlic

Two diagnostic models, reproducing circulation generated in a marginal sea by variable density, have been developed. The models’ domain is a 2D transverse section for which analytical solutions have been obtained. They describe the winter situation in the northern Adriatic, with a strong vertical mixing present and the density maximum dominating the centre of the basin. Both models employ Boussinesq-type

ABSTRACT High-resolution underway temperature and conductivity measurements collected by R/V Knorr during winter and spring 2003 are used to characterize errors associated with spatial aliasing in the northern and central Adriatic Sea. During winter, 99th percentile temperature, salinity and density errors were 0.62°C, 0.25 and 0.12kg/m3 (0.25°C, 0.10 and 0.05kg/m3) for sampling at 10km (5km) horizontal resolution, respectively. The corresponding values in spring were 1.31°C, 0.50 and 0.40kg/m3 (0.93°C, 0.25 and 0.22kg/m3) for the 10km (5km) sample spacing, respectively. The largest errors were associated with energetic regions over the shallow, western Adriatic, in front of the Po River mouth and off the tip of the Istrian peninsula. The deeper eastern basin exhibited smaller errors. The variability of errors in time and space reflected the variability of small-scale density features, characterized by wavelengths as small as 2km in winter and 1km in spring and being more pronounced in the western and northern parts of the Adriatic. As these results indicate that errors associated with undersampling can be considerable, they should be taken into account while planning future CTD measurements in the region.

ABSTRACT On the basis of two-month measurements of the bora wind at Senj, Croatia, with a 1 s temporal resolution, properties of the bora turbulence are inspected using the records of three bora episodes. The spectrum is divided into two parts: high-frequency turbulence (periods less than 1 min) and the low-frequency part (periods between 1 and 10 min) where pulsations appear. We have found that the high-frequency turbulence is generated locally by surface roughness and local wind shear. On the other hand, the low-frequency turbulence, i.e. the pulsations, seems to be independent of the local properties and can therefore be treated as an organized non-local effect. This is in accordance with the studies of the pulsations in the Boulder downslope windstorm. German Das Verhalten der Bora Turbulenz in Senj, Kroatien, während einer zweimonatigen Messperiode mit 1 sec Auflösung, wurde untersucht. Das Spektrum wurde unterteilt in einen Bereich hoher Frequenz (Perioden kleiner als 1 min) und einen Bereich niedriger Frequenz (Perioden zwischen 1 und 10 min). Hochfrequente Turbulenz wird im allgemeinen durch lokale Gegebenheiten, wie Oberflächenrauhigkeit und lokale Windscherung, verursacht. Die Turbulenz niedriger Frequenz des zweiten Bereichs dagegen scheint von lokalen Gegebenheiten unabhängig zu sein. Diese Pulsationen gleichen jenen, die in den Boulder Fallwinden gefunden wurden.