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Category Archives: Seasons
How is Wisconsin winter weather affected by La Niña?
Both La Niña and El Niño refer to big changes in the sea-surface temperature across much of the eastern tropical Pacific Ocean.
The water temperatures off the west coast of South America are typically 60 to 70 degrees. During a La Niña, these waters get as much as 7 degrees colder. These La Niña conditions recur every few years and last nine to 12 months, though some events have lingered for as many as two years. This cooling results from a strengthening of the winds over the tropical Pacific and its interaction with the underlying ocean waters. Continue reading
How unusual is the current warm spell?
After a rather persistently cold October in which the monthly averaged temperature was 3.5 degrees below normal, the first week of November has been remarkably pleasant with high temperatures at or above 68 every day since Election Day.
Naturally, such warm weather in November arouses curiosity regarding the frequency of November days with high temperatures at or above 70 degrees in Madison. Continue reading
Does the moon affect the weather?
Tides in the ocean are caused by the gravitational force between Earth and the moon. There are also atmospheric tides.
Lunar gravity affects the density of the thermosphere, which is the largest layer of the atmosphere. This is also where many satellites and the International Space Station orbit Earth. This lunar-induced drag is small, but it has to be included in the models used to predict the satellites’ orbits. The moon also affects the pressure at Earth’s surface. Continue reading
What is the status of the ozone hole?
Ozone occurs about 18 miles above the Earth’s surface.
Ozone is both caused by and provides protection from damaging ultraviolet energy emitted by the sun. The development of an atmospheric “ozone layer” allowed life to move out of the oceans and onto land.
The amount of ozone in the atmosphere is routinely measured from satellites. Typically, the Antarctic ozone hole has its largest area in early September and lowest values in late September to early October. This year it was measured to be one of the largest and deepest in recent years, covering just over 9 million square miles. Continue reading
Do the Rocky Mountains influence our weather?
Our string of beautiful days at the end of last week were related, believe it or not, to the presence of the Rocky Mountains hundreds of miles to our west. Last week, the atmospheric flow at levels just above the … Continue reading
