THE CROATIAN PART OF THE ADRIATIC SEA
General data
The Adriatic Sea is a deeply recessed bay of the Mediterranean, so that it belongs to semiclosed sea types. Parallel with the Adriatic basin, two big mountain chains extend, one on the Balkan and the other on the Apennine (Italian) peninsula. The Sea covers a surface of 138595 km. The coast length of the Croatian part of the Adriatic is 6278 km, of which land accounts for 1880 km and the islands for 4398 km.
Islands
In internal seawaters and territorial sea of the Republic of Croatia there are 1242 islands, islets and rocks. With such a multitude of islands, the Croatian coast is the most indented in the Mediterranean, after the Greek one. The Croatian coastland relief is suitable for terristric and electronic navigation. The islands with pronounced orographic conformations are also good orientation points.
Depths
The shallowest part of the Adriatic Sea is in the Trieste Bay, and the deepest one in the South-Adriatic basin (1233 m).
Temperature and salinity
The Adriatic is a warm sea with pronounced annual changes in sea surface temperatures. Winter temperatures range from 7 degrees C (in the extreme north-western part) to 14 degrees C (the Strait of Otranto), and in summer from 22 to 25 degrees C. The average Adriatic Sea salinity is about 38.30 C. The salinity in the northern part of the Adriatic is lower than in middle and south Adriatic because of the impact of Alpine rivers (the Po river in particular).
Surface currents
Sea currents have no major impact on open sea navigation safety. The current speed changes in certain areas and during some time periods. The average current speed is about 0.5 knots, but under certain circumstances, especially in narrow straits and in the vicinity of rivermouths, it can reach up to 4 knots.
Waves
The most frequent surface waves on the Adriatic are caused by bora, scirocco and the NW wind maestral (landward breeze blowing in the summer period). The characteristics of surface waves caused by the wind generally depend on the direction, speed and duration of the prevailing winds, the size of the area where these winds blow and seabed topography, which in the Adriatic give rise to much higher waves with scirocco than with bora, given the same wind speed and duration. The absolute open sea wave height maximum was recorded during a tempestuous scirocco in the north Adriatic and amounted to 10.8 m. In bora scenarios, the maximum wave height registered in northern Adriatic was 7.2 m.
Climate
According to the Köpen’s climate classification, the entire Adriatic area, except for its northern and northwestern part, is characterized by Mediterranean climate, with dry summers and humid autumn-winter periods ( Cs and Cfs classes). The northern and northeastern part of the Adriatic, i.e. the area from Venice to Rijeka, has some continental climate features, such as more pronounced annual air temperature changes and greater quantity of precipitation in summer.
Fog
On the whole Adriatic area the fog appears generally in the winter period (December-February). It is most frequent in the northern Adriatic, precisely in the Trieste Bay (more then 20 days a year) and on the Istrian west coast (10 to 20 days per year). In the remaining part it appears on average less than 5 days per year. In the Dubrovnik area fog is very rare (on average less than one day a year).
Winds
Winds blowing over the Adriatic generally depend on the distribution of barometric systems in the wider area. The most frequent winds in the Adriatic are the bora (NNE to ENE), scirocco (ESE to SSE) and maestral (WNW do NW). Besides, some winds blow from the north “oštro”, SW lebić, garbin, W pulenat, N to NW tramontana, E Levanter and there are also coast-oriented winds, burin or kopnenjak and zmorac. For a safe navigation it is extremely important to be well acquainted with the meteorological parametres, especially the wind. Given the climatic features and the orographic characteristics of the Adriatic islands and coast, abrupt weather changes are quite frequent, with the possibility of sudden wind blows (bora, scirocco, south-western winds, sudden summer storms). Under such circumstances navigation conditions get difficult and extremely dangerous, especially for small vessels.