عنوان مقاله [English]
Sea level variations in the Persian Gulf, the Oman Sea and the north of the Arabian Sea have been investigated. For this purpose, 365 daily satellite images provided by the TOPEX/Poseidon (T/P) and Jason-1 satellites were processed. Programming in Matlab software environment was also carried out for some parts of image processing.
The results of this research reveal that water level fluctuations are effectively observed only in the southern parts of the Persian Gulf; the southern region of Bahrain and Qatar, sometimes in the central and northern parts of the Persian Gulf; along the Bushehr Coasts, near the Arvandrood and Karoon rivers mouths in Abadan, and in the central parts of the northern Arabian Sea including; the eastern part of Muscat and Soor and also near the Chabahar coast of the Oman Sea. In other regions, water level fluctuations were very small and approximately about the average water level in the oceans in 1994.
These regions are important not only from the viewpoint of water level fluctuations, but also for other oceanographic and climatic parameters. Therefore, the characteristics of the water level fluctuations in the Persian Gulf, Oman Sea and the north of the Arabian Sea can be studied better by classifying and breaking these regions into the following main areas:
1. Bushehr coast to Arvandrood river mouth:
Southward currents resulting from northwesterly and westerly winds cause the water level to decrease on the Bushehr coast and thus to increase in the centeral region of the Persian Gulf.
2. Arvandrood river mouth and Kuwait and Saudi Arabia coasts:
Obtained results for this region indicate that water level in this area is relatively low and freshwater river runoff has a small impact on it, too.
3. Southern coasts of Bahrain and Qatar:
The large evaporation over the Persian Gulf and the shallowness of the water depth results in a high saline water (to a maximum value of about 50 psu) in this area. The dense water formed leaves this area through the deep part of the Strait of Hormuz and results in a decreasing water level in January, April, July, September and November. In February, March, May and October, thermal mixing causes density currents initiated from this area to weaken, a situation which leads to an increase in the water level along the southern coasts of Bahrain and Qatar during these months.
4. Central area of the Persian Gulf:
This region is separated from the North by a temperature and salinity front. Inflow from the Hormuz Strait in conjunction with down welling and areas of intense evaporation (> 40psu) create a cyclonic gyre in the center of the Persian Gulf. This gyre causes the water level to increase in this area in January, April, July, September and November.
5. The north of the Arabian Sea:
The northward flowing Somali current and the Oman coastal current are the most important and powerful currents in the Arabian Sea. The water level near 23°N is usually lower than the mean water level in the ocean.
6. Southern coasts of the Oman Sea:
The outflow from the Persian Gulf mainly goes toward this area. The water level has a weak fluctuation and is usually around zero in this area.
7. The line connecting Muscat to Chabahar and eastern coast of Chabahar:
The upwelling usually occurs in this area and the water level is usually greater than the mean water level in the ocean.
8. Rasal Hadd Area:
At the easternmost point of Oman (Rasal Hadd), interaction between the northward flowing Somali Current and Oman Coastal Current leads to forming the Rasal Hadd jet (also termed the Rasal Hadd front).
Moreover, a study of water level variations in 1994 results in distinguishing 3 different temporal patterns as; January pattern, October pattern and Calm pattern.
The results reveal that both of the maximum and minimum water levels observed in the south-east of Qatar were +57.5 cm and -47.5 cm, respectively. Water level fluctuations were intensified in October and January and were w