How is NAO calculated?
The standard NAO Index is calculated by taking the difference between normalized surface pressure anomaly from a 30 years mean of a northern and a southern station (Equation 1).
What does a positive NAO mean?
The positive NAO phase represents a stronger than usual difference in pressure between the two regions. Winds from the west dominate, bringing with them warm air, while the position of the jet stream enables stronger and more frequent storms to travel across the Atlantic.
What is NAO weather?
NOAA’s National Weather Service – Glossary. NAO. North Atlantic Oscillation – the NAO is a large-scale fluctuation in atmospheric pressure between the subtropical high pressure system located near the Azores in the Atlantic Ocean and the sub-polar low pressure system near Iceland and is quantified in the NAO Index.
How much cooler would Northwest Europe be without the North Atlantic Current?
Without the warm North Atlantic Drift, the UK and other places in Europe would be as cold as Canada, at the same latitude. For example, without this steady stream of warmth the British Isles winters are estimated to be more than 5 °C cooler, bringing the average December temperature in London to about 2°C.
What kind of weather results when the NAO is in its positive phase?
A large difference in the pressure at the two stations (a high index year, denoted NAO+) leads to increased westerlies and, consequently, cool summers and mild and wet winters in Central Europe and its Atlantic facade.
What would happen if the North Atlantic Current stopped?
If the currents were to stop completely, the average temperature of Europe would cool 5 to 10 degrees Celsius. There would also be impacts on fisheries and hurricanes in the region. The currents in the North Atlantic are part of a global pattern called thermohaline circulation, or the global ocean conveyor.
How cold would the UK be without the Gulf Stream?
The Gulf Stream brings warmth to the UK and north-west Europe and is the reason we have mild winters. Without this steady stream of warmth the British Isles winters are estimated to be more than 5C cooler, bringing the average December temperature in London to about 2C.
What happens if the North Atlantic Current collapses?
If that happened, it would likely be a climate disaster. It could freeze the far north of Europe, driving down average winter temperatures by more than 10 °C. It might cut crop production and incomes across the continent as much of the land becomes cooler and drier.
Is the North Atlantic drift weakening?
A gigantic ocean current, which transports heat around the globe and helps regulate weather patterns throughout the North Atlantic, appears to be slowing down. In fact, recent research has found that it’s currently at its weakest point in the last 1,000 years.
What would happen if North Atlantic Current stopped?
What happens to UK if Gulf Stream collapses?
The Gulf Stream brings warm water from the tropics to north-west Europe, helping to moderate the climate. If the Gulf Stream collapses, the study found that temperatures in the UK would drop by an average of 3.4°C.
How do you calculate the NAO index?
The NAO index is obtained by projecting the NAO loading pattern to the daily anomaly 500 millibar height field over 0-90°N. The NAO loading pattern has been chosen as the first mode of a Rotated Empirical Orthogonal Function (EOF) analysis using monthly mean 500 millibar height anomaly data from 1950 to 2000 over 0-90°N latitude.
What is the North Atlantic Oscillation (NAO)?
One of the most prominent teleconnection patterns in all seasons is the North Atlantic Oscillation (NAO) (Barnston and Livezey 1987). The NOA combines parts of the East-Atlantic and West Atlantic patterns originally identified by Wallace and Gutzler (1981) for the winter season.
What is the NAO loading pattern for EOF analysis?
The NAO loading pattern has been chosen as the first mode of a Rotated Empirical Orthogonal Function (EOF) analysis using monthly mean 500 millibar height anomaly data from 1950 to 2000 over 0-90°N latitude. For more information, please visit the Climate Prediction Center NAO page.
What are the characteristics of the NAO?
The NAO exhibits considerable interseasonal and interannual variability, and prolonged periods (several months) of both positive and negative phases of the pattern are common. The wintertime NAO also exhibits significant multi-decadal variability (Hurrell 1995, Chelliah and Bell 2005).