Atmospheric rivers are the largest freshwater transport mechanism on Earth

Rivers in the sky

A short introduction to atmospheric rivers, including a handy illustration on the science behind them, the phenomena that help transport water vapor from the tropics across the globe.

The largest river on Earth is actually in the sky

High above the canopy of the Amazon rainforest drifts an airborne river fed by the towering trees below. The trees pull water from their roots into their trunks, pushing any excess water out of their leaves and into the atmosphere as vapor. Watch this six-minute video to learn how.

Learn why water can take millions of years to be recycled via the hydrologic cycle

While a single drop of water spends an average of nine days in the atmosphere before precipitating back to Earth, it can spend thousands of years in the ocean before evaporating, and hundreds of thousands of years deep in rock layers before being released as steam in volcanic eruptions. Some water molecules have been trapped in Antarctic ice sheets for millions of years since they last moved through the water cycle.

The Great Lakes hold almost 20% of the world's surface freshwater

Formed by retreating glaciers, the Great Lakes system feeds Niagara Falls through the Niagara River. Together, the lakes contain about 23 quadrillion liters (5,400 cubic miles) of water, enough to cover the land portion of the continental US to a depth of 3 meters (9.84 feet).

Geological features on Mars' surface provide evidence of massive past flooding

The presence of river valleys, enormous canyons, and other structures carved by water on Earth suggests that water flowed abundantly across Mars' surface. The layering of rocks in the walls of these structures indicates the intensity and volume of these flows.

Tiny water droplets can blur a rainbow's colors into a foggy white

When sunlight enters water droplets, it can reflect from the inside and spread out into different colors, producing a series of colorful arcs—supernumerary bows—which we refer to as rainbows. For droplets a few hundredths of a millimeter in size, these arcs overlap onto each other, producing fogbows of white light.

How jet streams and US weather are affected by the El Niño-Southern Oscillation

Jet streams are predominantly west-to-east air currents in the atmosphere that mark the boundary between cold polar air and warm tropical air, where cells of atmospheric circulation meet. By disrupting the location of these circulations on two- to seven-year cycles, ENSO alters the probability of droughts, floods, and above- or below-average temperatures across the US.

Transpiration drives water movement through a plant’s vascular system

Water evaporates from the leaves, creating tension that pulls more water upward from the roots through the xylem—the equivalent of plant blood vessels. This process is supported by water molecules sticking to each other (cohesion) and xylem walls (adhesion).

Monsoons are large, seasonal shifts in wind driven by land-sea heating differences

Because land heats and cools faster than water, pressure differences form and create significant sea breezes. Moist air pulled onto land rises, condenses, and leads to substantial summer rainfall.

Hurricane Helene dumped enough water to fill Lake Tahoe

Alongside a rainstorm that moved into the region ahead of it, the hurricane released an unprecedented 40 trillion gallons of rain on the southeastern US, causing catastrophic flooding and at least 100 deaths. Meteorologists suggest climate change is exacerbating the severity of such events.

The weight of Earth's atmosphere is equivalent to a 33-foot deep, global ocean

Because air is made up of gas molecules with mass, it is not weightless. On the planet's surface, we are effectively living in what is the equivalent of the bottom of an invisible ocean of these particles pressing against us, just as water molecules do when we are submerged.

Why do flash floods occur?

Flash flooding can be more dangerous than traditional floods, occurring within the span of hours and exhibiting rapid currents. Here's how atmospheric conditions and geography combine to make some locations ripe for the disaster.

The Great Red Spot, Jupiter's largest storm, has existed for nearly 200 years

Despite decreasing in size, the anticyclone remains larger than Earth, rotating with winds up to 933 km/h. Its longevity may be because it is trapped between two opposite-flowing jet streams, which act like two conveyor belts.

Since 2022, two-thirds of data centers have been built in water-stressed areas

In residential evaporative cooling systems, 10% of consumed water is lost to evaporation compared to 80% in data centers. Although some companies have pledged to become water-positive—replenishing more freshwater than they consume—by 2030 through a transition to air cooling, only 10% of data center operators track water use across all their facilities.

As of 2025, the longest lightning bolt in the world spanned several states

Although the average bolt measures less than 16 kilometers (10 miles), the 2017 "megaflash" spanned 829 kilometers (515 miles) from eastern Texas to Missouri. Severe thunderstorms are common in the region, where warm, humid air from the Gulf collides with cool, dry air from the north, generating atmospheric instability.

How LA brought water to its booming population

By the turn of the 20th century, Los Angeles had grown from a dusty, crime-ridden pueblo into a thriving metropolis. The only problem was that it was growing too fast. Here's the story of how the booming town created a massive water infrastructure to redirect area rivers to its residents.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

View the 55 ECVs used to describe Earth's atmospheric conditions

Essential climate variables include physical, chemical, and biological variables that meaningfully contribute to Earth's climate and how it changes with time. Many of these variables influence one another through feedback mechanisms across Earth's atmosphere, hydrosphere, cryosphere, biosphere, and geosphere.

Oceans absorb 90% of warming from greenhouse gases

Oceans are providing increasingly more energy to power hurricane intensity. Current projections show rapid intensification is becoming more common, increasing the likelihood of Category 4 and 5 storms.

The Office of Water protects the nation's rivers, lakes and drinking supplies

The office develops national standards for safe drinking water, regulates wastewater treatment, and enforces the Clean Water Act. It partners with states and tribes to monitor pollution, protect wetlands, and restore aquatic ecosystems across the United States.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Tardigrades average about half a millimeter in size, with rear legs used for grasping

Their physiology and size, which is even smaller in the tun state, allow them to be carried by the wind and latch onto moist surfaces. They have been found in ocean trenches approximately 5 kilometers deep and at altitudes of six kilometers in the Himalayas.

Container ships are just a fraction of total traffic via the canal

While more container ships traverse the canal than any other type of ship, vessels carrying dry bulk goods, vehicle carriers, chemical tankers, passenger ships, and more also pass through the Central American passageway.

Satellite imagery of the massive seaweed blob in the Atlantic

A belt of sargassum seaweed that stretches from the west coast of Africa to the Gulf of Mexico is the largest on record for March.

Chemtrails are formed from condensing water vapor and soot from jet fuel

Conspiracy theories about the phenomenon—also known as contrails—began circulating in the 1990s, but have gained significant traction on social media platforms. Chemtrails are more common in high-humidity conditions, where they persist and form cirrus clouds.

Visualizing California's wine production

While Europe has France, Italy, and Spain, the US has California. The bulk of US wine production takes place in the Golden State, accounting for roughly two-thirds of the United States’ nearly 800 million gallons produced each year. This chart compares California and United States wine production from 1995 through 2022. Production in both has been trending down for several years, partially due to extreme weather events.

Egyptians called the Nile River the 'Ar,' meaning 'black'

The over 4,000-mile river would turn dark during its warm-season flooding as sediments flowed downriver. This nutrient soil, which would settle on the riverbank, was essential for farming in Egypt.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

The 19th-century painters of the Hudson River School were among the first American romantics, with portraits that displayed the natural beauty of the young country.

View the ten deadliest tornadoes in US history.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

The American Society of Civil Engineers' infrastructure report card gave the US a C in 2025, its highest grade since the project launched in 1998.

How Amazon operates a 'flywheel' business model, a self-reinforcing cycle that drives continuous growth

See how Budweiser's famous Clydesdales spend their days at Warm Springs Ranch, where roughly 70 to 80 of the beer brand's giant horses can be found at any given time.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

A small portion of The Winstons' 'Amen, Brother,' an obscure '60s gospel record, is the basis for thousands of hip-hop tracks, making it one of the most sampled records ever that's informally known as 'the Amen break.'

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in terms of casualties, forces mobilized, and displacement of civilians.