Precipitation

In the popular imagination, the Caribbean is paradise, an exotic place to escape to. But behind the images of balmy beaches and lush hotel grounds lies a crisis, the likes of which its residents have never experienced. Caribbean islands are in a water crisis, and their governments have warned that water scarcity may become the new norm. Within the past five years, every island in the region has experienced some sort of water scarcity. For example, Trinidad is experiencing its worst drought in recent memory, and residents are under water restrictions through at least the end of June 2024, with fines for anyone who violates the rules. Dominica, considered the nature island of the Caribbean for its mountain rain forests, is seeing a significant decrease in freshwater resources and increasingly frequent water shortages. In Grenada, known as the spice isle, drought has affected water systems throughout the island. Apartments in Havana, Cuba,...

Meteorologists have been talking for weeks about a snowy season ahead in the southern Rockies and the Sierra Nevada. They anticipate more storms in the U.S. South and Northeast, and warmer, drier conditions across the already dry Pacific Northwest and the upper Midwest. One phrase comes up repeatedly with these projections: a strong El Niño is coming. It sounds ominous. But what does that actually mean? We asked Aaron Levine, an atmospheric scientist at the University of Washington whose research focuses on El Niño. NOAA explains in animations how El Niño forms. What is a strong El Niño? During a normal year, the warmest sea surface temperatures are in the western Pacific and the Indian Ocean, in what’s known as the Indo-Western Pacific warm pool. But every few years, the trade winds that blow from east to west weaken, allowing that warm water to slosh eastward and pile up along the equator. The warm water causes...

Torrential downpours sent muddy water racing through streets in Libya, Greece and Spain and flooded parts of Hong Kong and New York City in September 2023. Thousands of people died in the city of Derna, Libya. Zagora, Greece, saw a record 30 inches of rain, the equivalent of a year and a half of rain falling in 24 hours. A few weeks earlier, monsoon rains triggered deadly landslides and flooding in the Himalayas that killed dozens of people in India. After severe flooding on almost every continent this year, including mudslides and flooding in California in early 2023 and devastating floods in Vermont and New York in July, it can seem like extreme rainfall is becoming more common. So, what role does global warming play in this? And importantly, what can we do to adapt to this new reality? A powerful storm system in 2023 flooded communities across Vermont and left large parts of the capital, Montpelier, underwater. John Tul...

It’s hard for most people to imagine more than 4 feet of snow in one storm, but such extreme snowfall events happen along the eastern edges of the Great Lakes. The phenomenon is called “lake-effect snow.” It starts with cold, dry air from Canada. As the bitter cold air sweeps across the relatively warmer Great Lakes, it sucks up more and more moisture that falls as snow. Canadian winds pick up moisture over the Great Lakes, turning it into heavy snowfall on the far shore. NOAA I’m a climate scientist at UMass Amherst. In the Climate Dynamics course I teach, students often ask how cold, dry air can lead to heavy snowfall. Here’s how that happens. How dry air turns into snowstorms Lake-effect snow is strongly influenced by the differences between the amount of heat and moisture at the lake surface and in the air a few thousand feet above it. A big contrast creates con...

Clouds form when water vapor – an invisible gas in the atmosphere – sticks to tiny floating particles, such as dust, and turns into liquid water droplets or ice crystals. In a newly published study, we show that microplastic particles can have the same effects, producing ice crystals at temperatures 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) warmer than droplets without microplastics. This suggests that microplastics in the air may affect weather and climate by producing clouds in conditions where they would not form otherwise. We are atmospheric chemists who study how different types of particles form ice when they come into contact with liquid water. This process, which occurs constantly in the atmosphere, is called nucleation. Clouds in the atmosphere can be made up of liquid water droplets, ice particles or a mixture of the two. In clouds in the mid- to upper atmosphere where temperatures are between 32 and minus 36 F (0 to minus 38 C), ice crystals...