Tag: geography

B.  Latent Energy

 Latent heat is the energy absorbed by or released from a substance during a phase change from a gas to a liquid or a solid or vice versa.  If a substance is changing from a solid to a liquid, for example, the substance needs to absorb energy from the surrounding environment in order to spread out the molecules into a larger, more fluid volume.  If the substance is changing from something with lower density, like a gas, to a phase with higher density like a liquid, the substance gives off energy as the molecules come closer together and lose energy from motion and vibration.

Absolute humidity is the actual amount of water vapour present in air. It is expressed as grams of moisture per cubic meter of air. It is calculated by finding the mass of water vapor in an area and dividing it by the mass of air in the same area. Absolute humidity may range from 0 gram per cubic meter in dry air to 30 grams per cubic meter when the vapour is saturated at 30 $^oC$. As the temperature of air increase, humidity also increases.

The phenomenon by which gaseous molecules convert from gaseous state to liquid state is called condensation. It is the process by which water vapor in the air is changed into liquid water. Condensation is responsible for the formation of clouds. That’s why it is crucial to the water cycle. These clouds produce precipitation which is the primary route for water to return to the Earth’s surface through rain. Condensation is the opposite of evaporation.

Humidity means the amount of water vapor present in the air. Time, place and temperature play important role in determining humidity. Amount of humidity changes with season and weather variation. Nearness to a water body,i.e, place plays an important role in determining humidity and lastly the moisture-holding capacity of air increases with increasing temperature.

Relative humidity is expressed as the amount of water vapor in the air as a percentage of the total amount that could be held at its current temperature. Absolute humidity is the measure of water vapor in the air, regardless of temperature. Relative humidity is cited in weather forecasts. It affects how we feel temperature. That’s why relative humidity is important.

The water vapor is one of the most variable gases in the atmosphere  which is present in small amount but is none the less very important. Water vapor plays an significant role in the insulating action of the atmosphere. The moisture holding capacity of the air varies in the direct proportion to its temperature. In other words the higher the temperature of the air,  the larger the capacity to hold moisture and vice versa. 

The droplets of water deposited on any cool surface by condensation of water vapour in atmosphere are known as dew. When temperature drops and objects cool down, dew is formed. The temperature at which dew forms is called the dew point. Location, weather, and time of day affect the dew point. Dew is more likely experienced by the humid areas than arid areas. It is mostly formed at night.

Degree Of Saturation: It is the percentage of water that occupies the pore spaces present in soil and is said to be a degree of saturation.

When the moisture saturated air comes across barriers such as mountains, it is forced to ascend and as it rises. Then condensation takes place and rainfall occurs. This type of rainfall is called relief rain or orographic rain.