50 Fun Facts About Monsoons

Traditionally, how is a monsoon defined?

The word is now also used for the seasonal swing in rainfall tied to the migration of the Intertropical Convergence Zone.

The English word "monsoon" ultimately derives from an Arabic word meaning what?

It reached English through Portuguese monção, and partly through early modern Dutch.

Which language did "monsoon" pass through on its way from Arabic into English?

Portuguese sailors were the first Europeans to work the Indian Ocean trade winds regularly.

The migration of which atmospheric feature is now considered the driver of monsoons?

Its northern and southern limits shift with the land–sea heating contrast each year.

Why do continents warm up more quickly than the sea in summer, setting up monsoon winds?

Water also mixes heat down to about 50 metres by convection, while rock and sand can only conduct it.

In summer, why does the air over heated land develop low pressure?

Cooler, higher-pressure air over the ocean then flows inland as a moist sea breeze on a continental scale.

Which direction do most summer monsoon winds have as their dominant component?

Winter monsoons are mostly easterly and tend to subside, bringing drought rather than rain.

The strengthening of the Asian monsoon has been linked to the uplift of which highland region?

It followed the collision of India with Asia about 50 million years ago.

How many major monsoon systems does the world have, according to the standard classification?

They are the West African, South Asian–Australian, North American and South American monsoons.

During which months does India's southwest monsoon occur?

It normally arrives at the end of May or start of June and fades in late September or early October.

Which arid region's summer heating creates the low pressure that draws the monsoon into India?

Moisture-laden winds from the Indian Ocean rush in to fill the void.

Which mountain range forces the monsoon winds to rise and drop their rain rather than pass into Central Asia?

Some parts of the subcontinent receive up to 10,000 mm of rain a year as a result.

Which Indian state is the first to receive rain from the southwest monsoon?

The Arabian Sea branch hits the Western Ghats there first.

What date is regarded as the official onset of the monsoon in India?

That is when the rains are expected to arrive in the southernmost state.

Into which two arms does the southwest monsoon split at the southern tip of India?

One runs up the Western Ghats, the other swings around the Bay of Bengal towards the eastern Himalayas.

Which town on the southern slopes of the Khasi Hills in Meghalaya is one of the wettest places on Earth?

Its average annual rainfall is 11,872 mm, and it recorded 1,003.2 mm in a single day in June 2022.

What is the average annual rainfall of the Khasi Hills town reputed to be the wettest place on Earth?

Two Colombian towns, Lloró and López de Micay, dispute its claim to be the wettest place on Earth.

Which town, also called Sohra, holds the records for rain in a single month and year?

It got 9,300 mm in July 1861 and 26,461 mm in the twelve months from August 1860.

How much rain fell in the Khasi Hills in July 1861, the record for a calendar month?

That is more than 30 feet of water in 31 days.

Roughly what share of India's annual rainfall comes from the monsoon?

A delay of a few days can hurt an economy in which agriculture employs about 70% of the population.

What term describes the sudden switch to wet, humid weather when the monsoon arrives in India?

The jet stream theory says the shift happens abruptly once the Tibetan Plateau heats up more than the Himalayas.

By what other name is the northeast phase, when cold air sweeps towards the sea, known?

Cold, dry air sweeps down from the Himalayas and picks up moisture over the Bay of Bengal.

Which Indian city is watered mainly by the northeast monsoon rather than the southwest one?

Tamil Nadu gets 50% to 60% of its rain from the northeast monsoon between October and December.

In which months does the northeast monsoon bring rain to southern Asia?

That is when the surface high-pressure system over the cooling northern landmass is strongest.

What is the northeast monsoon called in the Philippines?

It brings cool, dry air across the islands during the northern winter.

What is the East Asian summer rain belt called in China?

The name means plum rain; the same belt is called Jangma in Korea and Bai-u in Japan.

The East Asian monsoon's spring-summer rains are referred to in several languages as what kind of rain?

The belt moves north from Indochina in May to northern China and Korea by July.

Which dry, dusty trade wind is interrupted by the West African monsoon each summer?

The ITCZ reaches West Africa around June 22 and retreats south by October.

Which semi-arid African belt depends on the West African monsoon for most of its precipitation?

The monsoon comes from the temperature and humidity contrast between the Sahara and the equatorial Atlantic.

During which months does the North American monsoon occur?

It starts over Mexico and reaches the southwestern United States by mid-July.

Which narrow body of water is the main moisture source for the North American monsoon in Arizona?

Once the Sierra Madre Occidental forests green up, plant transpiration adds still more moisture.

By which other name is the North American wet phase commonly known?

Because so much of the affected area is the Mojave and Sonoran deserts, it is also called the Desert monsoon.

How much of their annual precipitation do most of northwest Mexico and the US Southwest get from the monsoon?

Rain typically reaches New Mexico and southeast Arizona in early July.

Which Californian mountains mark the western limit of the North American monsoon's push?

It rarely reaches the coast, so a wall of desert thunderstorms is often visible from sunny beaches.

What is the Australian monsoon commonly called?

Over three-quarters of northern Australia's annual rain falls in it, during the southern summer.

What share of northern Australia's annual rainfall falls during its monsoon?

The rainy season runs from September to February.

By what name is the so-called European monsoon better known?

Westerly winds from the Atlantic ease in spring and pick up again in June, loaded with rain.

How does an El Niño year usually affect India's southwest monsoon?

La Niña years bring particularly strong monsoons instead.

Which 1999-discovered climate pattern explains why the 1997 El Niño caused no drought in India?

Adding the EQUINOO effect also accounts for failed forecasts such as the acute drought of 2002.

Attempts to predict India's monsoon rainfall began after which disaster?

At least five prediction models now exist.

From which two directions do the seasonal winds along the Indian Ocean shores blow, half a year each?

Arabian Sea sailors trading between Africa, India and Southeast Asia were the first to observe the pattern.

How much rain fell in 24 hours on 17 June 2022 at the Meghalaya town reputed to be the world's wettest?

It beat the previous mark of 944.7 mm set on 7 June 1966.

How much rain did Guinness credit the reputedly wettest town in Meghalaya with in 1985?

That is roughly the height of an eight-storey building.

Which 2005 flood, brought on by monsoon rain, brought an Indian megacity to a standstill?

Assam, West Bengal and Bangladesh also flood almost every monsoon season.

Roughly how many years ago do many geologists believe the Asian monsoon first became strong?

Newer plant fossil and South China Sea sediment studies push the start back to 15–20 million years ago.

Which director general of observatories in India first observed the Southern Oscillation?

He noticed that when air pressure was high in Tahiti it was low in Darwin, Australia, a seesaw later tied to El Niño in the ocean.

The Southern Oscillation Index measures the pressure difference between Darwin and which island?

The oscillation turned out to be the atmospheric side of El Niño and La Niña, so together they are called ENSO.

By roughly when does the southwest monsoon normally cover all of India?

Withdrawal usually begins at the start of September and is complete by early October, when the northeast monsoon takes over.

About how long does India's northeast monsoon last after it bursts around 20 October?

Tamil Nadu gets 50 to 60 percent of its rain from this shorter, drier monsoon that picks up moisture over the Bay of Bengal.

Which upper-air jet replaces the subtropical westerly jet over India in summer, driving the monsoon?

Intense summer heating of the Tibetan Plateau is thought to be the critical factor in creating it, and a strong jet means a strong monsoon.