What is the Wettest Place on Earth?

Those who live along the “wet coast” – which is what people living in Puget Sound or the lower mainland of British Columbia and Vancouver Island affectionately call their home – might think that they live in the wettest place on Earth. Then again, people living in the Amazon rain forest might think that there lush and beautiful home is the dampest place in the world.

But in truth, all these places come up dry (pun intended!) compared to the one place that has held the title for wettest point on Earth many times in its history. And that place is none other than Mawsynram, India, which experiences an annual average rainfall of 12 meters. And yet, this curious region in northwestern part of the Indian subcontinent is an exercise in extremes, either drowning in rainwater, or starving for it.

Annual Rainfall:

When it comes to describing locations on planet Earth in terms of “wet”, some clarifications are needed. What we are talking about is average annual precipitation – i.e. rainfall, snow, drizzle, fog, etc. – measured in mm (or inches). This is necessary because otherwise, the “wettest” place on Earth would be the Mariana Trench, which has over 10,000 meters (36,000 feet) of water on top of it.

Cherrapunji, one of the wettest places on Earth. Credit: Public Domain
Cherrapunji, one of the wettest places on Earth. Credit: Public Domain

Also, based on rainfall. the wettest place on Earth has been known to change from time to time. In recent years, that title has gone to the town of Mawsynram, a village located in the East Khasi Hills district of northeastern, India. With an average annual rainfall of 11,872 millimetres (467.4 in), it is arguably the wettest place on Earth.

However, it is often in competition with the neighboring town of Cherrapunjee, which is located just 15 km (9.3 mi) to the west of Mawsynram in the East Khasi Hills district in northeastern India. The city’s yearly rainfall average stands at 11,777 millimetres (463.7 in), so it too has held the title.

The reason for these town experiencing so much precipitation has to do with the local climate. Situated within a subtropical highland climate zone, it experiences a lengthy and powerful monsoon season. In once instance, the monsoon season lasted for 2 years straight with no reported break in the rain!

Surprisingly, the high rainfall is a result of the region’s elevation and not the monsoon season alone. Huge amounts of warm air condense and fall as rain when they encounter the Khasi Hills. The topography of the region forces the very moist clouds up and down, forcing them to empty their accumulated water over the region.

Seven Sisters' falls, located in the East Khasi Hills district. Credit: Wikipedia Commons/Rishav999
Seven Sisters’ falls, located in the East Khasi Hills district. Credit: Wikipedia Commons/Rishav999

Other Locations:

Beyond northeastern India, there are several other locations on the planet that experience over 10 meters (32.8 feet) of annual precipitation. For instance, the town of Tutunendo, Colombia, experiences an average of 11,770 mm (463.38 in) of annual rainfall. The area actually experiences two rainy seasons a year, so precipitation is pretty much the norm.

Next up, there is Mount Waialeale, a shield volcano located on the island of Kaua’i on the Hawaiian Islands. As the the second highest point on the island, its name literally means “rippling water” (or “overflowing water”), and for good reason! This mountain has had an average of 11,500 mm (452 in) of rainfall since 1912.

However, in 1982, its summit experienced 17,300 mm (683 in), making it the wettest place on Earth in that year. And between 1978-2007, Big Bog – a spot in Haleakala National Park on the island of Maui, Hawaii – experienced an average of 10,300 mm (404 in) of rainfall, putting it in the top ten.

Wai?ale?ale (or 'Rippling Waters') Lake
Waialeale (or ‘Rippling Waters’) Lake, located atop Mount Waialeale on the island of Kaua’i, Hawaii. Credit: Wikipedia Commons/Volcantrek8

As already noted, the “wettest place on Earth” changes over time. This should come as no surprise, considering that weather patterns have been known to shift, not only in the course of an average year, but also over the course of centuries and millennia.

Nevertheless, those places that experience over 10 meters of precipitation are generally found within the tropical regions of the world, places known for experiencing intense and prolonged rainy seasons, and where lush tropical rainforests have existed for thousands of years. Here is a recent list of the top 10 locations.

But with anthropogenic climate change becoming a growing factor in planetary weather systems, this too could be subject to change. In the coming decades, and centuries, who’s to say where the most precipitation will fall on planet Earth?

We have written many interesting articles about rainfall and precipitation here at Universe Today. Here’s What are Tornadoes?, What is Tornado Alley?, Where do Hurricanes Occur?, What is a Warm Front?, and How Does Fog Form?

For more information, check out the US Geological Survey’s page on Precipitation: The Water Cycle and NASA’s Global Precipitation Measurement page.

Astronomy Cast also has an episode on the subject – Episode 226: Weather

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What is the Largest Desert on Earth?

Antarctica

When you hear the word desert, what comes to mind? Chances are, you’d think of sun, sand, and very little in the way of rain. Perhaps cacti, vultures, mesas, and scorpions come to mind as well, or possibly camels and oases? But in truth, deserts come in all shapes and sizes, and vary considerably from one part of the world to the next.

Like all of Earth’s climates, it all comes down to some basic characteristics that they share – which in this case, involves being barren, dry, and hostile to life. For this reason, you might be surprised to learn that the largest desert in the world is actually in Antarctica. How’s that for a curveball?

Definition:

To break it down, a desert is a region that is simply very dry because its receives little to no water. To be considered a desert, an area must receive than 250 millimeters of annual precipitation. But precipitation can take the form of rain, snow, mist or fog – literally any form of water being transferred from the atmosphere to the earth.

The Lut Desert of Iran, as observed from space by NASA's Earth Observatory. Credit: NASA
The Lut Desert of Iran, as observed by NASA’s Earth Observatory. It was here that the hottest temperature ever was recorded between 2003-9. Credit: NASA

Deserts can also be described as areas where more water is lost by evaporation than falls as precipitation. This certainly applies in regions that are subject to “desertification”, where increasing temperatures (i.e. climate change) result in river beds drying up, precipitation patterns changing, and vegetation dying off.

Deserts are often some of the hottest and most inhospitable places on Earth, as exemplified by the Sahara Desert in Africa, the Gobi desert in northern China and Mongolia, and Death Valley in California. But they can also be cold, windswept landscapes where little to no snow ever falls – like in the Antarctic and Arctic.

So in the end, being hot has little to do with it. In fact, it would be more accurate to say that deserts are characterized by little to no moisture and extremes in temperature. All told, deserts make up one-third of the surface of the Earth. But most of that is found in the polar regions.

Antarctica:

In terms of sheer size, the Antarctic Desert is the largest desert on Earth, measuring a total of 13.8 million square kilometers. Antarctica is the coldest, windiest, and most isolated continent on Earth, and is considered a desert because its annual precipitation can be less than 51 mm in the interior.

A Sun halo seen among the the landscape and ice flows of Antarctica. Credit and copyright: Alex Cornell.
A Sun halo seen among the the landscape and ice flows of Antarctica. Credit and copyright: Alex Cornell

It’s covered by a permanent ice sheet that contains 90% of the Earth’s fresh water. Only 2% of the continent isn’t covered by ice, and this land is strictly along the coasts, where all the life that is associated with the land mass (i.e. penguins, seals and various species of birds) reside. The other 98% of Antarctica is covered by ice which averages 1.6 km in thickness.

There are no permanent human residents, but anywhere from 1,000 to 5,000 researchers inhabit the research stations scattered across the continent – the largest being McMurdo Station, located on the tip of Ross Island. Beyond a limited range of mammals, only certain cold-adapted species of mites, algaes, and tundra vegetation can survive there.

Despite having very little precipitation, Antarctica still experiences massive windstorms. Much like sandstorms in the desert, the high winds pick up snow and turn into blizzards. These storms can reach speeds of up to 320 km an hour (200 mph) and are one of the reasons the continent is so cold.

In fact, the coldest temperature ever recorded was taken at the Soviet Vostok Station on the Antarctic Plateau. Using ground-based measurements, the temperature reached a historic low of -89.2°C (-129°F) on July 21st, 1983. Analysis of satellite data indicated a probable temperature of around -93.2 °C (-135.8 °F; 180.0 K), also in Antarctica, on August 10th, 2010. However, this reading was not confirmed.

McMurdo station at night. Credit: m.earthtripper.com
Antarctica’s McMurdo Station at night. Credit: m.earthtripper.com

Other Deserts:

Interestingly, the second-largest desert in the world is also notoriously cold – The Arctic Desert. Located above 75 degrees north latitude, the Arctic Desert covers a total area of about 13.7 million square km (5.29 million square mi). Here, the total amount of precipitation is below 250mm (10 inches), which is predominantly in the form of snow.

The average temperature in the Arctic Desert is -20 °C, reaching as low as -50 °C in the winter. But perhaps the most interesting aspect of the Arctic Desert is its sunshine patterns. During the summer months, the sun doesn’t set for a period of 60 days. These are then followed in the winter by a period of prolonged darkness.

The third largest desert in the world is the more familiar Sahara, with a total size of 9.4 million square km. The average annual rainfall ranges from very low (in the northern and southern fringes of the desert) to nearly non-existent over the central and the eastern part. All told, most of the Saraha receives less than 20 mm (0.79 in).

However, in northern fringe of the desert, low pressure systems from the Mediterranean Sea result in an annual rainfall of between 100 to 250 mm (3.93 – 9.84 in). The southern fringe of the desert – which extends from coastal Mauritania to the Sudan and Eritrea – receives the same amount of rainfall from the south. The central core of the desert, which is extremely arid, experiences an annual rainfall of less than 1 mm (0.04 in).

Temperatures are also quite intense in the Sahara, and can rise to more than 50 °C. Interestingly, this is not the hottest desert on the planet though. The hottest temperature ever recorded on Earth was 70.7 °C (159 °F), which was taken in the Lut Desert of Iran. These measurements were part of a global temperature survey conducted by scientists at NASA’s Earth Observatory during the summers of 2003 to 2009.

In short, deserts are not just sand dunes and places where you might come across Bedouins and Berbers, or a place you have to drive through to get to Napa Valley. They are common to every continent of the world, and can take the form of sandy deserts or icy deserts. In the end, the defining characteristic is their pronounced lack of moisture.

In that respect, the polar regions are the largest deserts in the world, with Antarctica narrowly beating out the Arctic for first place. And going by this definition – i.e. cold, arid, and with little to no precipitation – we’re sure to find some particularly big deserts elsewhere in Solar System. After all, what is Mars if not one big, cold, arid, and extremely dry climate?

We have written many articles about the Earth for Universe Today. Here is What Percent of the Earth’s Land Surface is Desert?, What is the Driest Place on Earth?, What is the Hottest Place on Earth?, What is the Earths’ Average Temperature?

Want more resources on the Earth? Here’s a link to NASA’s What is Antarctica?, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

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