Correct Answer - Option 2 : Heavy Rainfall
On the basis of origin rainfall is classified into three types:
- Conventional rainfall.
- Orographic rainfall or relief rainfall.
- Cyclonic rainfall or frontal rainfall.
All these three types of rainfall are found in India.
| Type of rainfall |
Characteristics |
| Mountain Rainfall |
- Mountains can have a significant effect on rainfall.
- When air reaches the mountains, it is forced to rise over this barrier. As the air moves up the windward side of a mountain, it cools, and the volume decreases.
- As a result, humidity increases, and orographic clouds and precipitation can develop. When the air descends the leeward side, it warms and is drier because the moisture in the air was wrung out during the ascent. This area with a lack of moisture is known as a rain shadow.
- The slope of the mountain has a direct bearing on the possibility of precipitation. This is borne out by the Ghats of Karnataka where the mountains are gently sloping, compared to the steep slopes of the Ghats in Maharashtra and Kerala.
|
| Convectional Rainfall |
- It is caused by the conventional ascent of warm and humid air to great heights. Due to excessive heating of the earth’s surface in the summer months, vertical air currents are produced.
- As the surface air rises, it expands and cools and eventually gets saturated. This is followed by condensation and precipitation.
- Rainfall in the doldrums is of convectional nature.
|
| Cyclonic Rainfall |
- When two large masses of air currents having unequal densities and temperature came into contact, the rising warm moist air mass reaches above the colder one.
- The rising warm moist air condenses to form clouds and then causes heavy rainfall.
- Such rainfall associated with thunder and lightning is also called frontal rainfall.
|
Rainfall intensity is classified according to the rate of precipitation, which depends on the considered time. The following categories are used to classify rainfall intensity:
-
Light rain — when the precipitation rate is < 2.5 mm (0.098 in) per hour
-
Moderate rain — when the precipitation rate is between 2.5 mm (0.098 in) – 7.6 mm (0.30 in) or 10 mm (0.39 in) per hour
-
Heavy rain — when the precipitation rate is > 7.6 mm (0.30 in) per hour, or between 10 mm (0.39 in) and 50 mm (2.0 in) per hour
-
Violent rain — when the precipitation rate is > 50 mm (2.0 in) per hour
Heavy rainfall is found in a few areas of Meghalaya that are also covered under monsoon rainfall. It is not a specific type of rainfall found every time, intensity can vary from time to time.
