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Category Archives: Phenomena
Why is the wind often calmer at night than during the day?
The cycle of daytime heating and night time cooling explains why, under most circumstances, calm winds are near the surface at night.
The wind usually increases with height above Earth’s surface. The wind several thousand feet above the ground is almost always stronger than that experienced near the ground. Friction causes the wind close to the ground to move more slowly. Friction decelerates the wind in the same way a rough road surface slows down a bicycle. Continue reading
Category: Meteorology, Phenomena
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How can there be frost on the ground when my thermometer reads 36 degrees?
This set of circumstances does not mean that her thermometer is faulty and in need of replacement. Instead, it reflects a nearly daily reality that goes undetected for most of the year until the cold season. It turns out that the air does not radiate heat away nearly as well as the solid ground beneath it. As a consequence of this difference, given 13 hours of nighttime with clear skies, the ground radiates a lot more energy away (and cools rapidly) while the air above struggles to cool as efficiently. Over those many hours, this difference results in a big difference between the ground temperature and the air temperature even as little as 5 or 6 feet above the ground. Continue reading
Category: Meteorology, Phenomena
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Are hurricanes intensifying more quickly?
Hurricane intensities are classified using the Saffir–Simpson scale, which rates hurricanes on a scale of 1 to 5 based on the damage their winds would cause upon landfall. Major hurricanes are those classified as Category 3 and higher on this … Continue reading
Category: Meteorology, Phenomena, Tropical
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What are the trade winds?
On the morning of August 3, 1492, Christopher Columbus set sail on his first voyage to the Americas. He sailed south along the west coast of Africa, searching for the easterly “trade winds,” discovered earlier by the Portuguese, that would propel his fleet westward toward what he thought was India.
The trade winds are a component of a global-scale tropical circulation feature known as the Hadley cell. This cell is driven by the fact that the equator is heated more intensely than latitudes to its north and south, resulting in the production of collections of thunderstorms girdling the globe roughly along the equator. Continue reading
Can wildfires generate weather?
Fires require something to burn plus air to supply oxygen and a heat source to get the fuel to its ignition temperature.
Once a fire starts, weather is one factor of how it will spread and if it will grow. The important weather factors are temperature, wind and humidity. Warmer temperatures allow fuels to ignite quickly, and low humidity keeps the fuel dry and easy to burn. Wind brings oxygen to the fire and also can help to spread it. Continue reading
Category: Meteorology, Phenomena, Severe Weather, Weather Dangers
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