The Physical Study of Vertical Structure of Temperature, Salinity and Density Layer Structure Between Persian Gulf and Oman Sea

Always oceanographers pay attention to layer structure in the sea environment. Creation of layer structures is because of some phenomenons like double diffusion, internal waves, turbulence modular mixing. In this paper with examination of vertical structure of temperature, salinity and density between Persian Gulf and Oman Sea in different seasons, layer structures appear clearly. Also, countors of the same physical parameters show the existence of regular structure which prove internal waves resulting from the Persian Gulf and flow into the Oman Sea. The exchange flow through the Stait of Hormus results from horizontal density gradient between the Persian Gulf and Oman Sea. In winter the density ratio ( ) Rρ in this nearshore region is about 0.7 and in offshore region is 0.2. this shows that in this area, double diffusion forms layer structures which have horizontal variations as well as in the vertical. Coastal topography also seems to affect the double diffusion processes and leads to variations of layering in horizontal directions especially between near and offshore regions.


Introduction
Always oceanographers pay attention to layer structures in the sea environment. Creation of layer structures is because of some phenomenon's such as; double diffusion, internal waves, turbulence modular mixing. When salinity and temperature distribution in water column has a upside down effects with regard to density distribution, very interesting structures can be created in water column which is called double diffusion convection. Two types of regimes are existed in this convection: a) When salinity and warm water stays above cool and fresh water, the finger regime is occurred.
b) Layering regime is occurred when warm and salinity waters stay below cool and fresh water or water column with constant salinity gradient which is heated. In this situation; one layer in coast due to inconsistency in temperature gradient effect will be created and convection is performed. In result, a thin layer is composed. 156 often are known as Termohaline convection. These phenomenon in laboratories in salinity solutions with different temperature in laboratories in salinity solutions with different temperature or in melted alloys are occurred and also are known as double diffusion convection. When a fluid has density layering, this fluid has not any movement. For example, when a warm layer water stays above cool water, fluid will be constant and has not any movement and there is no any other mechanism in this situation, which could dominate the floating force. The composition which its diffusion is faster than the other, can ascend and mixing in vertical point will be created.
This process is known as double diffusion convection. Thus; coefficient of density diffusion is negative, that is; in allover of density of vertical stratification in increased [1,2].
In ocean environments, due to the difference of salinity and temperature in different depth of waters, double diffusion convection is observed. The occurrence of double diffusion convection is due to three basic factors permanently and naturally in most of oceans and seas: a. Temperature difference of surface and depth waters.
b. Salinity thickness difference which are exist in these waters. c. Diffusion difference of warmth and salinity.

The Area to be Studied
Persian Gulf is a half-closed sea which is located in a low depth region. In this area, the rate of evaporation is extremely greater than the rate of raining and discharges of rivers. Evaporation velocity in  Confusion processes due to vertical mixing in Persian Gulf was studied and discussed by Huge and Hunter. The showed that time scope for vertical mixing in water column is 3 days in winter and 17 in summer. Summer can cause increasing the stratification effects which can prevent in mixing of water column.

Inception Conditions of Double Diffusion Convection
The simplest way; investigation of system between two According to second dimensional line constancy analysis and by using Business approximation without friction effect, we can refer to the equations of movement and salinity and temperature diffusion for both composition with similar scopes.
With the solution of the above equations and boundary conditions ( , S=T=0 at Z=1,0) stable and unstable surroundings are obtained according to Figure 3 in two diagrams of Figure 4 for areas of Persian Gulf, constant boundaries of double diffusion convection of finger regime were drawn which similar to it, was reported by others [4,5].

Calculations and Results
In this research; the analysis of temperature and salinity profiles which are obtained by CTD frameworks during the cruising Mont Michael's ship (1992) was used ( Figure 5). Density ratio ( R ρ ), is key parameter in the study of double diffusion convection. Infact, double diffusion convection with density rate for temperature and salinity profiles is calculated by implies for constant gradient for both S and T. and there is no convection.