Temperature relations in the Adriatic Sea
Abstract
All the available temperature data of the Adriatic sea collected so far have been statistically dealt with.
The first chapter deals with the analysis of the temperature data of the sea surface along the east coast collected from 22 stations. The considerable difference in temperature observed between the north and the rest of the Adriatic is suggested as due to the greater continental effect in the former region. The influence of certain meteorological elements like cloudiness and cold wind on the sea temperature is also shown.
The higher values of air-sea temperature difference are found when the influence of the land on the air temperature is stronger, ie. when there is a stronger penetration of the cold continental air over the Adriatic.
The second chapter deals with (the temperature of the open sea surface. Seasonal temperature fluctutations have been presented by means of charts of average distribution for four characteristic months. Some characteristics of these charts have been explained by means of the known properties of the current system. In the mid Adriatic transverse profile (Kaštelanski zaljev - Gargano) during Spring and Summer the minimum temperatures appear near the islands Hvar, Vis and Palagruža. It is pointed out that this might be related to the water divergence and upwelling at those places. In Autumn the lowest temperature in the profile is found along the west coast and in Winter along the east coast. This has also been connected with the system of currents and the wind influence (jugo and bura respectively) and their possible resultant water upwelling. The long term variations of the differences between the temperature of the open and coastal sea have been assigned to the influence of advection which is more prominent in the open sea. The Trieste - Hvar air pressure difference also shows a parallel course indicating the cause of the advection intensity fluctuations.
In the third chapter, the vertical temperature distribution is given. The average values calculated for the whole Adriatic are used in a preliminary calculation of the evaporation of the Adriatic in the warm and cold periods of the year (28 and 70 cm respectively). The lower limit of the termocline for the north, middle (coastal as well as open) and south Adriatic has been layer up and it is found to vary from 20 to 40 m. In the layer up to the termocline the maximum temperature appears in Summer and the minimum in Winter. The intermediate layer is characterised by the phase shift in the reaching of the maximum, which occurs in Autumn. The lower limit of this layer is at 100 m in the mid Adriatic, whereas it is at 300 m in the south. This layer can be to some extent identified with the previously dynamically identified intermediate layer which is characterised by water advection from the Mediterranean. The temperature of the bottom layer is not influenced by the mixing with the upper layers; it is rather under the influence of the advection of the heavy Winter water from the north Adriatic. In the north Adriatic the vertical temperature gradient is greatest in the surface layer and appears in Spring, whereas in the mid and south Adriatic it is highest below the surface and appears in Summer.
