Subscribe Now

At the tropopause (the point in altitude where the lowest part of Earth’s atmosphere, the turbulent troposphere, transitions into the more stable stratosphere), which is located at about nine miles up, bands of 200 mile-per-hour air currents flow around the world while periodically meandering north and south. These air currents are known as jet streams. [...]

In Southeast Arizona, there has been a marked increase in wintertime rainfall since 1977, which has resulted in a three-fold increase in shrub cover. Prior to this period, grasses had dominated the region’s vegetation system. As the shrubs have moved in, so have species of small pocket-mice, which are replacing large kangaroo rats. One species [...]

While forests fires may be the most visible and dramatic events that reshape North America’s forests, outbreaks of insect “pests” actually affect an area 45 times larger than that affected by fire. Generally, insects attack trees weakened by things like drought, wind storms, and fire, as healthy trees are usually able to fend-off attacks from [...]

A warmer atmosphere results in an “amplification” of the water cycle. Some areas of the world are net importers of rainfall (such as tropical rainforests), while some are net exporters (such as oceans around the tropics). The “amplification” of the cycle means that dry regions become drier, and wet regions become wetter. During the 20th [...]

Autumn (March to May) rainfall in southeast Australia is important for soil moisture and river recharge because the region is dependent on reliable water sources for cereal crop production. Since 1950, there has been a 40 percent decline in the region’s average autumn rainfall. This has been linked to fewer occurrences of La Niña events, [...]

A warmer atmosphere results in an “amplification” of the water cycle. Some areas of the world are net importers of rainfall (such as tropical rainforests), while some are net exporters (such as oceans around the tropics). The “amplification” of the cycle means that dry regions become drier, and wet regions become wetter. During the 20th [...]

Getting a break from exposure to hot temperatures is important for preventing heat related illnesses. While people usually associate extreme daytime temperatures with heat stroke, if it does not cool sufficiently during the night, the body will not get a break from the heat. In North America over the last 50 years, average nighttime low [...]

Is it possible for droughts to become more common even if annual rainfall amounts increase? Overall annual precipitation in the lower 48 states has been increasing since the early 20th century, and since the 1970’s it has been increasing in the Eastern United States by about one-inch per decade. Over the last forty years, this [...]

The summer of 2003 was one of Europe’s warmest on record and maximum sea surface temperatures (SSTs) in the Mediterranean were well above average (by about 2.5 degrees Fahrenheit). These temperatures were the highest recorded between 1972 and 2004.  Also during this period, years when the maximum water temperature was above average were years when [...]

The northeastern quadrant of the contiguous United States, defined as the area from Minnesota south to Missouri and then east to Maryland and north to Maine, has been experiencing changes in its precipitation regime. While the average annual number of “wet” days (or days when rain falls) in that region declined by about four percent [...]

The tropical Pacific basin is one of the planet’s warmest ocean regions, with surface water temperatures rarely falling below 83 degrees Fahrenheit. These perennially warm temperatures provide the fuel for tropical cyclone formation, and the strongest cyclones on record have formed here. Because these waters are already above the threshold for tropical cyclone formation, slight [...]

Convective available potential energy (CAPE) is a measure of how much energy is available for storm development (CAPE is measured by the number of joules present in a kilogram of air). Generally, the hotter and more humid conditions are, the more CAPE is present. A collection of atmospheric conditions, including some CAPE, are necessary for [...]

The El Niño Southern Oscillation (ENSO) cycle, or the cyclical movement of heat in the tropical Pacific Ocean, affects the upper atmosphere over the Atlantic Ocean. This affects both the frequency of Atlantic tropical cyclone formation as well as the positioning of the region’s high and low pressure centers that steer the tropical cyclones. La [...]

The El Niño-Southern Oscillation (ENSO), or the cyclical movement of heat in the tropical Pacific Ocean, affects atmospheric phenomena throughout the world. The cycle affects the strength and position of the Pacific Jet Stream, an upper atmosphere wind current that flows from the Pacific over North America. During La Niña phases of the cycle, the [...]

The North Atlantic Oscillation (NAO) is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. the low pressure center is especially low and the high pressure center [...]

The North Atlantic Oscillation (NAO), which is part of a large system known as the Arctic Oscillation, is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. [...]

The North Atlantic Oscillation (NAO) is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. the low pressure center is especially low and the high pressure center [...]

Rainfall patterns in the United States are shifting. Overall, precipitation in the lower 48 United States has increased by ten percent since 1910. Since the 1970’s, the South Bend Area has been experiencing rainfall increases at a rate of 0.3 to 0.6 inches per decade. This extra rainfall has come in the form of extreme [...]

Rainfall patterns in the United States are shifting. Overall, precipitation in the lower 48 United States has increased by ten percent since 1910. Since the 1970’s, the Sioux City Area has been experiencing rainfall increases at a rate of 1.0 to 1.5 inches per decade. This extra rainfall has come in the form of extreme [...]

Rainfall patterns in the United States are shifting. Overall, precipitation in the lower 48 United States has increased by ten percent since 1910. Since the 1970’s, the Milwaukee Area has been experiencing rainfall increases at a rate of 0.3 to 0.6 inches per decade. This extra rainfall has come in the form of extreme events; [...]