Archives
Categories
WeatherGuys Links
Author Archives: WeatherGuys Editor
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
Comments Off on Why is the wind often calmer at night than during the day?
Comments Off on Why is the wind often calmer at night than during the day?
Does fall give any hints about the intensity of the coming winter?
Each winter we keep track of the areal extent of air colder than 23 degrees Fahrenheit at the 850 mb pressure level (about 1 mile above sea-level) around the entire Northern Hemisphere. This measure allows us to characterize the intensity of the winter season with respect to the lower tropospheric temperature.
Over the past 75 seasons there has been a systematic decrease in the December-January-February, or DJF, average areal extent of about 4.6%, and this is an unequivocal sign of global warming, measured in the winter season. Continue reading
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
Comments Off on How can there be frost on the ground when my thermometer reads 36 degrees?
Comments Off on How can there be frost on the ground when my thermometer reads 36 degrees?
What is the National Climate Assessment?
The U.S. National Climate Assessment is mandated by the Global Change Research Act of 1990. The assessment is conducted about every four years and is an authoritative scientific analysis of climate change risks, impacts and responses in the U.S.
The nation this month completed the Fifth National Climate Assessment, or NCA5. The National Oceanic and Atmospheric Administration is the administrative agency for NCA5 and certifies that the report meets Information Quality Act and Evidence Act standards. The assessment is an extensive process that includes internal and external review from federal agencies, the general public and external peer review by a panel of experts. Continue reading
Category: Climate, History, Seasons, Severe Weather
Comments Off on What is the National Climate Assessment?
Comments Off on What is the National Climate Assessment?
What is a gale wind?
A gale is a strong, sustained wind impacting maritime weather.
