The increase in humidity saw dense fog envelop Indore region on Sunday morning, which led to the delay in arrival of five trains to the city. Around 96 per cent humidity was recorded in the morning hours in the region which later dropped to 39 per cent in evening.
“The increase in humidity during morning hours and presence of clouds led to dense fog in the region,” said Virendra Singh, scientific assistant at Indore metrological department. The humidity has been on rise in the region since five days.
According to the met department, minimum temperature was recorded at 13.5 degree Celsius, 3 degrees above normal temperature on Saturday. It was fifth consecutive day when minimum temperature remained three degrees above normal.
The met official however said that the minimum temperature will start to drop in the week ahead. On Sunday, the maximum temperature also dropped by two degrees to 24.3 degrees Celsius.
How fog is formed?
A fog is formed whenever there is a temperature difference between the ground and the air. When the humidity is high enough and there is enough water vapor or moisture fog is sure to form.
One way of fog formation is due to infrared cooling. Infrared cooling happens due to the change of seasons. During the summer the ground absorbs solar radiation. When the seasons change the mass of warm moist air collides with the cooler air that is now prevalent. This cause is the water vapor in the air mass to condense quickly and fog is formed. This fog is often called radiation fog due to the way it forms. This kind is the most common type of fog.
In Indore it happened because of a day of warm weather combined with high humidity. This normally is followed by dropping of temperatures.
What is humidity? Absolute humidity is the mass of water vapour divided by mass of dry air in a volume of air at given temperature. The hotter the air is, more water it can contain. Relative
humidity is ratio of current absolute humidity to highest possible absolute humidity. When relative
humidity is high, the body feels hotter than actual temperature. If relative humidity is low, we feel cooler than actual temperature because our sweat evaporates much faster, cooling us off.