Dew Point And Saturation Point: Relationship And Detailed Facts

The saturation point is when the density of the water vapor in the air is 100% fully saturated at a constant pressure condition.

The temperature at the dew point is lower than the atmospheric pressure. If the temperature at a dew point and the atmospheric temperature are equal then it is said to be a saturation point. The saturation point results in the formation of the dew and fog.

Is Dew Point and Saturation Point Same?

The dew point and saturation point are not the same; there is a variation in the temperature and the density of the system at both points.

At saturation point, the density of the water vapors in the air is very high and the temperature is equal to the atmospheric temperature. If the temperature of the system falls below the atmospheric temperature then the tiny condensed water vapors will condense further to form the drops of water, well, the dew point and saturation point are almost the same.

The radiation energy received by the Sun is incident on the water bodies and plants. This heat energy breaks the intermolecular distance and increases the kinetic energy of the molecules. These molecules then escape from the water bodies and plant through the process called evaporation and transpiration respectively. These water vapors are emitted into the atmosphere and evaporate at a height until the kinetic energy of the molecules is completely utilized.

The water vapors get mixed into the dry air forming fog. As the density of the water vapors in the air increases, the air reaches the saturation point keeping the pressure constant. During this point, the temperature of this region is equal to the atmospheric temperature. If the temperature of the saturation region goes below the atmospheric temperature then the dew point occurs and the tiny water vapors begin to condense further forming droplets of the water as fall down due to gravity.

The saturation point of water vapors in the air; Image Credit: Pixabay

Is Dew Point Saturated?

Indeed! The dew point is saturated and the condensation of water vapors is carried further at a temperature slightly below the saturation point.

The dew point occurs due to the fully saturation of the water vapors in the atmosphere and thus these water vapors condense to form drops of water due to which the temperature of the system falls slightly below the dew point. Hence at a dew point, the atmosphere is fully saturated with the highest density of the water vapors in the air.

The temperature of the air at this point is cooled down a bit while the pressure remains constant. The rate of formation of the water drops is exactly the same as the rate of evaporation of water to form the vapors.

As the density of the water vapors in the atmosphere increases gradually the temperature of the air falls down maintaining the same pressure condition. At this point, the density of the air has reached the saturation point and the condensation of the water vapor further results in the formation of the water drops, this is called a dew point.

What is the Relationship between Saturation And Dew Point?

At saturation point as well as the dew point, the density of the water vapors in the atmosphere is very high.

Both depend upon the moisture in the air, the amount of evaporation and transpiration, the temperature and pressure condition, and the radiation received during the day timing.

The saturation of the water vapors in the atmosphere results in the condensation of the vapors back into a tiny water droplet. At saturation point, the density of the water vapors in the air is so high that it begins to condense maintaining the same pressure conditions. The phenomenon of the condensation of the tiny water droplets into the water drops is called a dew formation. Thus dew point is seen as a consequence of the saturation point.

Dewdrops on the leaves; Image Credit: Pixabay

Moreover, the vapor pressure felt at the saturation as well as the dew point is the same. As the air reaches the saturation point, the vapor pressure is held constant and the temperature falls down gradually to reach the dew point.

Difference between Dew Point and Saturation Point

The saturation point results in the formation of fog while it is a condition necessary for the dew point to occur.

At saturation point, the temperature of the system is equal to the atmospheric temperature and on the contrary, the dew point is attained when the temperature goes slightly below the atmospheric temperature while the vapor pressure remains constant.

The liquid and vapor phases are in an equilibrium state at a saturation point, while on attaining the dew point the vapors condense into the liquid state. Hence, another main difference between the dew point and the saturation point is the phase change process. The vapor state does not change until the air reaches the saturation point till it reaches the dew point where there is a fall in the temperature of the air and the conversion of the vapors to the liquid state takes place.

Graph of Density of Water Vapor v/s the Temperature giving Relation between Dew Point and Saturation Point

Here is a graph of the density of the water vapor in the atmosphere v/s temperature indicating the variation in the density of vapor in the atmosphere as the temperature changes.

dew point and saturation point
Graph of the density of water vapor v/s temperature

The graph clearly shows that as the density of the water vapors reaches the saturation point it does not change while the temperature of the system falls down maintaining the constant vapor pressure and attaining the dew point. The temperature TA denotes the atmospheric temperature. At saturation point, the temperature of the air is equal to the atmospheric temperature and the same is shown in the above graph.

At a dew point, the water vapors condense and convert the vapors back into the liquid phase. The condensation of the vapors decreases the concentration of the vapors in the atmosphere and thus the density of the water vapors drops exponentially.

Frequently Asked Questions

How dew point is different from the dew?

The dew point is a temperature at which the concentration of the water vapors in the atmosphere is densely saturated.

If the temperature of the air goes below the dew point temperature then the tiny water vapors will condense further to convert vapors into the water phase thus leading to the formation of dew.

How precipitation is different from the saturation point?

The precipitation implies the acceleration of the condensed matter back on the ground.

While the mixture of the water vapors into the dry atmosphere and uphold of the water vapors into the air results in attaining the saturation point of the vapors at the constant pressure condition.

How does the presence of aerosol affect the saturation point of the air?

The aerosols are the suspended particles that remain in the atmosphere this could be smog, fog, dust particles, radiated emissions, etc.

The evaporated water vapors get easily soaked in these aerosol particles in the air thus the air reaches the saturation point very sooner increasing the density of the air.

Does the temperature affect the saturation point?

In reality, the temperature of the system does not affect the saturation point directly at the time of saturation.

The amount of evaporation of water depends upon the radiation and the heat energy received by the water bodies during the daytime. If the temperature of the system is high then the energy lost in the form of vapors will be high and thus the saturation point will be attained more rapidly.

Also, please click to know about Dew Point and Altitude.

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