Table of Contents
What does a positive NAO mean?
The NAO is in a positive phase when both the sub-polar low and the subtropical high are stronger than average. During positive NAO phases, the increased difference in pressure between the two regions results in a stronger Atlantic jet stream and a northward shift of the storm track.
What is the cause of NAO?
The North Atlantic Oscillation (NAO) index is based on the surface sea-level pressure difference between the Subtropical (Azores) High and the Subpolar Low.
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 is NAO weather?
North Atlantic Oscillation (NAO), an irregular fluctuation of atmospheric pressure over the North Atlantic Ocean that has a strong effect on winter weather in Europe, Greenland, northeastern North America, North Africa, and northern Asia.
What happens during the weakening of NAO?
Simply put the negative NAO creates an “atmospheric road block.” The westerly winds weaken, resulting in limited upper air flow over the entire North Atlantic extending all the way to the US East Coast. The reduced flow also keeps cold air locked into the eastern US.
What is Southern Oscillation?
El Niño and the Southern Oscillation, also known as ENSO is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean. The Southern Oscillation describes a bimodal. variation in sea level barometric pressure.
Why is the NAO important?
Especially during the months of November to April, the NAO is responsible for much of the variability of weather in the North Atlantic region, affecting wind speed and wind direction changes, changes in temperature and moisture distribution and the intensity, number and track of storms.
What is the current status of the NAO?
The North Atlantic Oscillation (NAO) is currently neutral and is predicted to remain negative to neutral as pressure/geopotential height anomalies are predicted to remain mostly positive across Greenland the next two weeks.
What does the NAO do to the ocean?
The NAO determines the speed and direction of the westerly winds across the North Atlantic, as well as winter sea surface temperature. The NAO index is the difference in normalized sea level pressures between Ponta Delgadas (Azores) and Akureyri (Iceland).
What causes Southern Oscillation?
These motions – rising in the west, sinking in the east – are connected through easterly trade winds near the surface and a westerly wind aloft, forming the Walker Circulation. Fluctuations in the position and intensity of the Walker Circulation cause the Southern Oscillation.
What is the role of Southern Oscillation?
The El Nino-Southern Oscillation (ENSO) is an irregular cycle of change in wind and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. ENSO is known to strongly influence the rain in many countries in South America and East Asia.
What causes a negative NAO?
The negative NAO phase represents the reverse with a weaker than usual difference in pressure. Winds from the east and north-east are more frequent, bringing with them cold air, while the adjusted position of the jet stream leads to weaker and less frequent storms.