What is a negative Arctic Oscillation?

What is a negative Arctic Oscillation?

The harsh winter weather was attributed to a negative Arctic Oscillation, which is a climate pattern that influences weather in the Northern Hemisphere. A very persistent, strong ridge of high pressure, or ‘blocking system’, near Greenland allowed cold Arctic air to slide south into Europe.

What causes negative Arctic Oscillation?

The basics of pressure When the difference is less strong, the AO is in its negative mode. The AO can persist in either phase anywhere from days to months. Pressure differences manifested in the AO affect Earth’s atmosphere and people’s lives, particularly in winter.

How do the positive and negative phases of the Arctic Oscillation effect weather in the eastern US and Florida?

The Arctic Oscillation (AO), has been shown to have a big influence on temperatures across the eastern two-thirds of the United States during the winter months. The negative phase allows cold air to plunge into the Midwestern/Eastern United States and Western Europe, and storms bring rain to the Mediterranean.

What happened to the polar vortex 2021?

Globes show show 10-millibar geopotential heights—an indicator of air pressure—for (left) December 26, 2020 as the polar vortex began to weaken, (middle) on January 5, 2021 when the stratospheric winds reversed sign, and (right) on January 15, 2021 during the sudden stratospheric warming event.

Will the polar vortex return in 2021?

When the jet stream gets wavy, it can dip farther south, bringing cold air and winter storms with it. The January 2021 event pushed the polar vortex from its normal position over the North Pole all the way over to Europe and Siberia, nearly pulling it apart multiple times in the process.

Is there another polar vortex coming in 2021?

The polar vortex, composed of lofty winds that circulate atop the globe each winter, largely stayed put in the Arctic last year. But in 2021 the winds have weakened, allowing frigid air to spill out of the polar regions. A blast of Arctic air is now destined for a large swath of the U.S. beginning by week’s end.

Why is spring so cold 2021?

This winter weather is exacerbated by sinking winds in the Arctic and La Niña. The March 2021 cold snap was caused by frigid Arctic air tumbling downwards, bringing freezing temperatures and wintery weather to the rest of the world. In most parts of the U.S., this means more snow and winter weather overall.

Will it be a hard winter 2020?

The U.S. 2020-2021 Winter Forecast The Almanac is calling for a ‘Wild Card Winter’ in some southern parts of the country, meaning conditions could turn from mild to serious or visa versa. The west and southwest regions should see a dry, generally mild winter this year, without too many surprises.

Is there going to be snow 2020?

ALBERTA. A bitterly cold winter is expected across Alberta with above normal snowfall across the southern half of the province. However, the first half of December will be a dramatic contrast to the rest of the season, as it will feel more like autumn with very mild temperatures and even some record warmth.

Is the Arctic oscillation in a positive or negative phase?

Over most of the past century, the Arctic oscillation alternated between positive and negative phases. Data using a 60-day running mean has implied the oscillation has been trending to more of a positive phase since the 1970s, though it has trended to a more neutral state in the last decade.

How does the Arctic oscillation affect the polar vortex?

The positive or negative mode of the Arctic Oscillation changes the shape of the polar vortex, as shown by these examples from the winters of 1988 to 1989 and 2009 to 2010. Note that the color coding for atmospheric pressure is not for high or low pressure, but for higher or lower pressure than average for a given region.

How is the AO index of Arctic oscillation obtained?

AO index is obtained by projecting the AO loading pattern to the daily anomaly 1000 millibar height field over 20°N-90°N latitude. The AO loading pattern has been chosen as the first mode of EOF analysis using monthly mean 1000 millibar height anomaly data from 1979 to 2000 over 20°N-90°N. For more information on the AO, please see CPC’s AO page.

How does the AO affect the North Pole?

When the AO is in its positive phase, a ring of strong winds circulating around the North Pole acts to confine colder air across polar regions. This belt of winds becomes weaker and more distorted in the negative phase of the AO, which allows an easier southward penetration of colder, arctic airmasses…

What is a negative Arctic Oscillation? The harsh winter weather was attributed to a negative Arctic Oscillation, which is a climate pattern that influences weather in the Northern Hemisphere. A very persistent, strong ridge of high pressure, or ‘blocking system’, near Greenland allowed cold Arctic air to slide south into Europe. What causes negative Arctic…