Impact of Local Climatic Elements on Short-term Fluctuations of Sea Level Case Study: The Northern Coasts of Hormuz Strait -Bandar Abbas

As fluctuations of ocean and sea levels on coasts especially on coastal shapes and also process of morphogenesis of it, study of these fluctuations and its causes is needed. Level fluctuations can be divided to short-term and long-term. Waves derived from wind, pressure from metrological elements and temperature are short-term elements and surface winds are most important among others on temporary sea level. Water level changes in Hormuz strait area has been studied based on the data obtained from Bandar Abbass station during 1990-1998 periods. The length of Persian Gulf as a branch of The Indian Ocean is about 990 km, its maximum width is about 330 km (at Hormuz strait about 60 km) and its depth is about 100 m. The Persian Gulf is connected to Oman Sea via Hormuz strait.Materials and MethodsIn the present study, first of all, correlations between atmospheric elements such as pressure, temperature and the density of wind energy (independent variables) with sea level changes are studied by drawing the graphs and then linear regression graphs of pressure and temperature and the density of wind energy (seasonal) with sea level changes for a 9-year period (1990-1998) and their correlation coefficient are calculated. Furthermore, wind energy calculated using empirical relationships in the area and equation of sea level changes prediction has beenobtained for the coast of this region.Results and discussionSea level changes: the results of the present study show that sea level changes can be divided into two types in the coast of this region. Temporary changes lasting from a few hours to several days and permanent changes that is seasonal and may last for several months. Air pressure changes: air pressure changes at sea level is inversely related to the water level changes in this region that means that with decreasing air pressure at sea level, water level increases and vice versa (pressureinversion effect). Using data from meteorological stations and tidal station in the region, it is distinguished that there is a strong negative correlation (-0.83) between air pressure and sea level.Effects of air temperature: air temperature has two contrastive and seasonal effects on water level. There is a strong positive correlation (0. 812) between air temperature and sea level in Bandar Abbass. In summer, air temperature increase due to seawater heating causes reduction in seawater volume, increasing salinity and density of seawater as well as increasing the volume and reduction in seawater density due to volume expansionof seawater. In winter, air temperature decrease due to seawater temperature reduction causes reduction in seawater volume, increasing the density of surface waters due to volume contraction of seawater. Effects of wind characteristics: it is distinguished that wind velocity and consequently wind power is low in the Spring based on average of wind velocity and wind power graphs in different months of the year. In summer, the power and velocity of wind increase and in autumn the increasing status will continue and in the winter they reach to a peak. In general, whenever the wind velocity was high, the wind power increased too. By studying the simultaneous wind velocity variations, the density of wind energy with sea level changes in this region, it is distinguished that sea level coming up by the start of wind (landward) and reaches to a peak and sea level retard with wind velocity decrease and come back to its former level.ConclusionIt would be concluded that there is significant correlations between temperature and pressure with sea level fluctuations and these fluctuations are seasonal. With maximum value in summer and minimum in spring and winter. When the wind starts to blow, sea levels swells and reach to maximum.An average of correlation coefficient for Bandar Abbass station was 0.733 that showed the relation between wind velocity and sea level fluctuations; these fluctuations will influence on erosion process into delta in coastal