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The term cloud condensation nuclei (CCN) is a fancy way of describing the tiny particles that even smaller water vapor droplets cling to as raindrops form. Once enough water vapor droplets gather on the nuclei, raindrops fall. This is a critical part of Earth’s water cycle, which moves water from the oceans to the land, [...]

The area around Vermont’s Green Mountains is a “transition zone” between the boreal forests in Canada, which are dominated by conifer species that are better adapted to the extreme winter cold, and the broadleaf forests that are familiar to residents of the eastern U.S. Higher elevation areas of the Green Mountains are significantly colder and [...]

In the Southwest U.S., prolonged dry episodes are defined as periods of two months or longer when daily precipitation falls below one millimeter. Trivia Question: Have such prolonged dry episodes become more or less common over the past 60 years? a)    More common b)    Less common c)    No change The correct answer is b. Despite [...]

In northern China, how much rain falls each year is controlled by the strength of the Asian Monsoon – the system of seasonal winds that bring moist marine air onto land during the summer and cold dry air out to sea during the winter. When the monsoon system is strong, there is ample rainfall and [...]

In Brief: Higher elevation areas are experiencing the overall global trend of wind speed “stilling” more acutely than surrounding lowlands. Wind speeds in the mid-latitudes have shown a downward trend over the past 30-50 years, a phenomenon known as “stilling.” Any trends in wind speed have implications for the water cycle, ecosystems and wind energy [...]

In Brief: Persistently cool conditions in the eastern tropical Pacific during the Middle Ages led to drought in the southwestern United States. Conditions in the tropical Pacific influence weather throughout the world. On a cycle of two to seven years, the eastern tropical Pacific moves from cool (La Niña) conditions to warm (El Niño) conditions. [...]

Better understanding how fluctuations in climate have affected regional wildfire frequency over the past few centuries may help to improve our ability to predict severe wildfire seasons. Some of the West’s older groves have experienced dozens of wildfires over the past few centuries. The trees that survived these fires recorded black scars in their annual [...]

The temperature/pressure difference between the equatorial regions and the poles is at its maximum during the winter months. The energy this difference generates is thought to power the “storm tracks,” or the bands in the mid-latitudes where east to west traveling storms (cyclonic high and low pressure systems) are most common. The storm track over [...]

Snow is both a product of the weather and a weather maker. It has long been recognized that snow exhibits a cooling effect on local and regional scales. Snow reflects more sunlight than bare ground, meaning that it absorbs less energy. More snow cover also means soils stay moist for longer following the spring melting [...]

Snowfall and snow cover have direct effects on transportation, soil freeze/thaw cycles, water availability, flood frequency, water quality, wildlife, forest fires and more. Far from being just a passive product of prevailing climatic conditions, snow cover also influences climate by changing the surface albedo, the amount of solar radiation a surface reflects. The presence of [...]

While commonly considered two separate lakes, Lakes Michigan and Huron are actually hydrologically one body of water – they are connected at the Straits of Mackinaw and rise and fall in unison. Since 1980, Lake Michigan-Huron has been warming and annually averaged surface temperatures are now 3.6 degrees Fahrenheit warmer than they were in the [...]

When put in 2000 US dollars, freezing rain (ice storm) events in America caused an estimated 16.3 billion dollars in total losses between 1949 and 2000 due to downed power lines, downed trees, agricultural losses, transportation accidents and medical costs from injuries due to slippery conditions. Freezing rain events are most frequent in the Northeast, [...]

Once water is evaporated from the ocean or a moist land surface, it may spend days traveling through the air. Complicated systems of winds at different levels of the atmosphere can transport moisture (as well as other gases and dust) from the point of origin to remote locations thousands of miles away. While about 30 [...]

In Brief: Higher temperatures are reducing America’s snowfall, with a few regional exceptions. Snow is not just an inhibitor of holiday travelers, nor is it just a passive product of prevailing weather conditions. Snow is a weather maker in and of itself. Snow-covered ground reflects far more of the sun’s radiation than it otherwise would [...]

In Brief: Less ice cover on the Great Lakes is contributing to more snow regional lake effect snow. Over much of the U.S., the 20th century warming trend means less snow and more rain. In most areas, the lack of cold limits snowfall, but this is not true in the Great Lakes region. Here, temperatures [...]

December is East Coast Winter Storm (ECWS) season. These storms are powered by warm water that flows from the Gulf Stream. The Gulf Stream current flows along the Eastern Seaboard past Florida and the Carolinas before reaching Cape Hatteras, where the warm water heads out into the Atlantic. ECWS’s travel northward along the coast causing [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than average. When the eastern Pacific is in an El Niño phase, the northwestern [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than average. When the eastern Pacific is in an El Niño phase, the southern [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than normal. When the eastern Pacific is in an El Niño phase, the southwest [...]

On average, about 20 trillion grams (20 teragrams) of dust are suspended in Earth’s atmosphere, where the dust particles stay for an average of 21 days. Dust is an important part of Earth’s climate – dust affects how clouds develop and how much sunlight reaches the Earth, which affects rainfall. The Dust Bowl of the [...]