Final answer:
The question is about the state of the Arctic Oscillation (AO) in the JFM period since the early 1980s and how it influences weather patterns in the Northern Hemisphere.
Step-by-step explanation:
The subject of this question is Geography and it is appropriate for High School students. The question is asking about the state of the Arctic Oscillation (AO) in the period of January, February, and March (JFM) since the early 1980s.
The Arctic Oscillation is a natural climate pattern characterized by fluctuations in atmospheric pressure over the Arctic and mid-latitude regions. It has a significant influence on weather patterns and climate conditions in the Northern Hemisphere.
When the AO is in a positive phase, there is stronger than average westerly winds circulating around the Arctic, which tends to keep cold air confined to the polar region. This usually results in milder and less severe winter conditions across much of the mid-latitudes.
On the other hand, when the AO is in a negative phase, the polar winds weaken, allowing cold air to spill southward, leading to colder and more extreme winter weather in parts of North America, Europe, and Asia.