Rain is common, but why does it rain: Why is it raining: the rainiest cities on Earth and how do they differ by type? Which cities are the rainiest on Earth and which are the driest and why?
What is rain?
Rain is an important link in the water cycle in nature. This seemingly simple phenomenon can be explained. For example: The sun’s heat heats the Earth’s surface, causing water to evaporate. Then it rises from the ground, changing from a liquid to a gaseous state. In the atmosphere, the vapor forms clouds. Wind enhances this process. In mid-latitudes it is impossible to visually see the described process.
But in the tropics, where the humidity is high, it is possible. It’s fascinating to watch how the moisture forms into bubbles that swirl and rise up.
Why does it rain? 🌧️
There are four main reasons for the formation of rain:
- The presence of water vapor in the air: The air must contain water particles; otherwise, clouds will not form even under the influence of solar heat.
- Updrafts of air: Sunlight heats the surfaces of bodies of water and the ground, provoking the evaporation of moisture, which, along with the air current, rises into the atmosphere.
- The collision of warm and cold air currents (atmospheric fronts). The temperature difference between air currents creates an atmospheric front. It has a contrasting temperature and causes rain.
- Elevated areas of relief: Starting at the foot of hills, mountain ranges, and elevated plateaus, moisture-saturated air rises without changing direction. As it ascends, it cools and condenses into clouds.
Statistics show that the most rain is recorded in areas of low pressure with upward air flow. The least amount of rain occurs where atmospheric pressure is high and air flow is descending.
From a physics perspective, this can be explained as follows: as air rises, it cools by 1°C for every 100 meters in dry air, and by 0.6 degrees in humid air due to internal heat. The ground, grass, and trees release heat only when reaching the dew point. This is when the temperature of the surrounding environment is such that the vapor contained in the air condenses into dew. When the dew point exceeds 20°C, it becomes muggy. The warmer it is, the higher the vapor rises.
Visually, clouds are light and white, allowing sunlight to pass through. The more moisture there is in a cloud, and the lower the temperature of the cloud, the darker it becomes. Such clouds are called rain clouds. At heights where the surrounding air temperature reaches -30°C, water vapor droplets turn into crystals, i.e., they transform into ice particles. When the cloud descends, these ice particles, approaching the Earth and entering warmer layers of the atmosphere, melt, becoming droplets again. In cold weather, they fall as snow.
Where does rainwater go?
Rainwater saturates the soil with moisture, penetrates crevices, and replenishes reservoirs.
According to the water cycle in nature, it evaporates again, rises and forms clouds. They eventually bring rain again. And so it goes in a circle.
Types of rain:
- Regular rain: Water precipitation that falls in small amounts throughout the warm season. It usually lasts about two hours. The average size of the droplets is 0.5 mm. If their size is smaller, this type of rain is called drizzle.
- Mushroom rain: This is rain during which the sun continues to shine, not hiding behind clouds. This type of rain gets its name because mushrooms begin to grow actively after it.
- Autumn Rains: Seasonal rains characteristic of the autumn period. They are accompanied by a decrease in air temperature. They last for a long time, slowly, with varying frequency and a constant increase in the volume of precipitation. They can last for several days. The cause of prolonged autumn rain is layered clouds that tightly cover the sky.
- Off-Season Precipitation: These are types of precipitation that do not correspond to a specific season. For example, sleet in winter or hail in summer. Hail does not often fall without rain and is accompanied by a sharp, almost instantaneous drop in atmospheric temperature. This phenomenon is dangerous. Hail can damage homes, cars, and injure people. Its size can be larger than a chicken egg.
- Downpour: A downpour is very intense precipitation. It can start suddenly, lasts for a short time, but falls heavily and abundantly. It can cause minor flooding and undermine basic non-foundation buildings. In 90% of cases, it is accompanied by a thunderstorm. It most often occurs in spring and summer.
- Tropical Downpour: A phenomenon characteristic of climatic zones with high humidity and strong winds. Tropical downpours are strong, abundant, and prolonged, often causing destruction, leading to floods and landslides. The force of its flow can wash away cars and buildings.
- Acid Rain: A dangerous chemical type of precipitation. This is toxic rain, the droplets of which have absorbed substances from production, vehicle emissions, and combustion products. After it, a whitish or reddish coating often appears on the leaves. Young plants may even die, and people may experience burns to their mucous membranes, skin or hair. Such rain is most dangerous for people with allergies.
The Rainiest Cities on Earth
Lloró, Colombia
The city of Lloró in northwestern Colombia is aptly called the “weeping” city. Precipitation occurs so frequently that local residents are forced to protect their homes with special waterproof coverings. The annual amount of precipitation is 13,000 mm per year, but it can be even more.
Mawsynram, India
The name of the Indian village Mawsynram translates from Sanskrit as “abode of the clouds.” It rains there almost year-round, with an annual precipitation level of no less than 12,000 mm. The reason for this is the winds. They carry clouds to Mawsynram, forming them over the Indian Ocean and Bay of Bengal.
Cherrapunji, India
Cherrapunji is a small high-altitude town in the Indian state of Meghalaya. It is located at an altitude of 1,313 meters above sea level and is famous worldwide for its heavy summer downpours. During the season, more than 11,777 mm of precipitation falls, while in winter, surprisingly, there is drought and a significant lack of water.
Mount Waialeale, Kauai, Hawaii, USA
The dormant volcano Waialeale is prized by locals for being a natural rain collector. 11,684 mm of precipitation falls annually on its slopes. The volcano itself is usually completely invisible, as it is hidden by thick fog.
Hokitika, New Zealand
The town of Hokitika is located on the banks of the Cropp River in New Zealand. The Cropp River is only 9 kilometers long, but the humidity in the area is very high. Therefore, more than 11,500 mm of precipitation falls annually.
Kibdo, Colombia
The city of Kibdo is located in the west of Colombia. It rains there on average 304 days a year. Annual precipitation is 10,700 mm per year. It is the main source of fresh water, which is collected in containers placed on the roofs of houses.
Debundja, Cameroon
The village of Debundja in Cameroon is another one of the rainiest places on the planet. More than 10,000 mm of precipitation falls there each year.
Mount Emei, China
Mount Emei in China is called the sea of clouds because it is drenched with heavy rains annually. It receives 8,100 mm of precipitation. This is the rainiest geographical point in China.
Andagoya, Colombia
An amazing place in Latin America known for its consistent temperature. The warmest month is April (+27.7°C), while the coldest is November (27°C). Moreover, due to its proximity to the ocean, nearly 7,000 mm of precipitation falls here each year. By the way, most of the rainfall occurs at night.