The study and exploration of physical processes in the ocean, the interaction of ocean with the atmosphere and the role of the ocean in earth's ecosystems and climate are referred as physical oceanography in the scientific discipline. Some major themes of physical oceanography include ocean wave phenomena, the exchange of momentum, freshwater, heat, gasses between the ocean and the atmosphere and much more. Important applications of physical oceanography are in Global climate studies and coastal systems. Physical oceanography is the one sub-domain of oceanography. However, other may include chemical, geological and biological oceanography.

Methods and techniques of physical oceanography

Many direct and indirect methods are used by oceanographers for measuring currents, momentum and other physical activities inside the ocean. Some of them will be discussed. Determining the three-dimensional circulation of the oceans as a function of time is the main objective of the oceanographers.

1. Sensors to observe the ocean:

Diverse sensors are used to observe the oceans and are being improved constantly. Two categories are sensors are used:

I.   In-situ sensors, which are physically in contact with the water. In-situ sensors are used to determine the seawater density, salinity, In-situ temperature, pressure, velocity. The complete class of in-situ methods to measure currents can be referred as serendipitous current measurements. They include tracking the drifting object's location, either at the depth or at the surface, mariner's reports, and interpreting the spread of deliberately-released, or natural, chemical tracers.

II. Remote sensors, which are used to observe the oceans from space through satellites. Remote sensors are used to determine the sea-surface height and sea-surface temperature.

2.  Platforms to observe the Ocean

The platforms used to deploy the sensors by oceanographers are diverse in nature. The most important platforms include the ships, autonomous devices such as drifters, floaters, and gliders which are submerged to the depth of the oceans with in-suite sensors. Other devices are moorings used to suspend instruments in the water at the fixed place (Richard E. Thomson, 2014). Navigation through which the position of things and person's around and inside the ocean is determined.

3.  Salinity measurement

Salinity is the important factor which defines a particular sea water, along with pressure and temperature. Following methods are used to determine the salinity of the water.

I.  Electrical conductivity method: An alternative method to measure the salinity was realized by Knudsen in 1902. The International Ice patrol developed the first conductivity salinometer for the sea water.

II.Chemical titration method: The volumetric method developed by Prof. Martin Knudsen for estimating the chloride content. Inconstancy with the composition of sea water, salinity can be estimated through the chloride content.

III. Refractive index method: Pulfrich designed the immersion refractometer with the thermostated sea-water sample to determine the salinity through the measurement of the optical refractive index. The refractometer to measure the salinity in-situ has also been developed.

IV.  Density method: Through measuring the density of sea water sample, the salinity can be determined. The hydrometer was used to measure the density of sample sea-water.

Equations and Models for the motions in the ocean

1.  Transformation of Newton's second law: To express mass is constant; the motion of the sea has to refer the equation of continuity. The same amount of water coming out of volume unit as there is flowing in, for that the density of the water particles should not be changed. We will not deduce the mathematical expression for this principle, but an integrated form of the equation has already been presented (Duff, 2016). The Newton's second law fulfilled the equation of continuity. The Newton's second law includes the terms like absolute acceleration, an inertial reference frame. 

2.Geostrophic currents: The Straits of Dover separates England and France is joined eastto west with the French coast to the south. The Straits resides 51 degrees North and 35 kmWide. The water is well mixed by tidal currents and strong winds. The mean Geostrophiccurrently is toward the east. Now the question arise here is-

I. If the mean geostrophic current is 0.2 ms -1, what is the slope of the sea surface?

II. Is the sea surface higher on the French or English side?

III. How much higher?

3.Hydrostatic equilibrium: The Earth's atmosphere is the gas which is most familiar in everyday's life. Most of the observable features of the atmosphere can be explained by isothermal and adiabatic gas laws. So let's start with the hydrostatic equilibrium of the atmosphere. Hydrostatic equilibrium is also known as hydrostatic balance when it is at rest. This is because of gravity which is balanced by a pressure gradient force.

4. Wind currents: Wind currents start at the equator and are circular patterns of moving area. Important factors like low and high-pressure zones and tilt of the earth are also affected how the wind blows. The movement of air in a particular direction through a mass of air which is not moving much is called wind currents. The surface of the earth vary in different places - it is encrusted in oceans, mountains, plateaus, etc. When hot air rises up, cool air rushes to take the place of the hot air. The main cause of wind is the difference in temperature between two regions due to uneven heating of the earth by the sun. During the hot summer, land in India becomes warmer than the sea. The air over the land evaporates, creating a vast low-pressure region. The wind of the area of high-pressure blow in both directions towards the equator and towards the pole.

Conclusion

It can be thus concluded that physical oceanography is the leading science through which various physical activities inside the ocean can be observed, measured and can be beneficial in determining the atmospheric situations and currents. Department of physical oceanography continuously works on the new inventions associated with the movements observed in the oceans. The science is interesting for the people who love to be some adventurous in their life. It is strongly recommended that government should be more prompt in providing the knowledge to coming generations by introducing the science in academic studies.