Jet streams are fast-flowing air currents located at high altitudes in the atmosphere, significantly influencing global weather patterns and air travel routes.
Jet streams occur primarily in the upper troposphere, approximately 7 to 12 kilometres above the Earth's surface. They are defined as narrow bands of strong wind that move from west to east due to the temperature gradient between polar and tropical air masses. The most significant jet streams include the Polar Jet, which forms near the boundaries of cold polar air and warm tropical air, and the Subtropical Jet, which is associated with the subtropical high-pressure systems.
The movement of jet streams is influenced by various factors, including the Earth's rotation (the Coriolis effect), seasonal changes, and geographical features such as mountain ranges and large bodies of water. As the sun heats the Earth's surface unevenly, warm air rises near the equator while cooler air descends closer to the poles. This temperature difference drives the atmospheric circulation patterns, leading to the formation and movement of jet streams. Throughout the year, these jet streams can shift in position and intensity, particularly influenced by seasonal changes and climatic events.
Jet streams play a crucial role in shaping weather patterns across the globe. They act as steering currents for storm systems and can influence precipitation, temperature changes, and severe weather events. For example, when the Polar Jet dips southward, it can bring cold Arctic air into lower latitudes, resulting in colder temperatures and winter storms in regions like the United States. Conversely, when the jet stream is positioned to the north, warmer air can dominate, leading to heatwaves in areas such as Southern Europe.
One notable example of jet stream influence is the "Beast from the East," which refers to the extreme cold weather experienced in the UK and Europe in March 2018. The Polar Jet stream shifted significantly southward, allowing cold air from Siberia to flow into Western Europe, leading to heavy snowfall and widespread disruption.
Another example is the impacts of El Nino and La Nina events on the jet streams. During an El Nino event, the warmer ocean temperatures in the equatorial Pacific can alter the position and strength of the tropical and polar jet streams, consequently affecting weather across North America and other parts of the world.
Understanding jet streams is vital not only for forecasting weather but also for optimising air travel routes, as airlines often rely on these high-altitude winds to enhance fuel efficiency and reduce travel time.
