Upper Atmospheric Circulation Flashcards
What is the Constant isobaric surface?
An elevated surface in the atmosphere on which all points have the same pressure, usually 500 mb. Along this constant-pressure surface, isobars mark the paths of upper-air winds.
What is the Rossby wave
An undulating horizontal motion in the upper-air westerly circulation at middle and high latitudes.
Rossby waves occur along the polar front, where colder air meets warmer air, and bring tongues of cold air southward, with warmer tropical air moving northward. The development of Rossby waves begins with undulations that then increase in amplitude to form waves (Figure 6.13, page 160). As these disturbances mature, circulation patterns form in which warmer air and colder air mix along distinct fronts. These wave-and-eddy formations and upper-air divergences support cyclonic storm systems at the surface. Rossby waves develop along the flow axis of a jet stream.
What are Jet streams?
The most prominent movement in upper-level westerly wind flows; irregular, concentrated, sinuous bands of geostrophic wind, travelling at 300 km · h−1.
The most prominent movement in the upper-level westerly geostrophic wind flows are the jet streams, irregular, concentrated bands of wind occurring at several different locations that influence surface weather systems
What are the typical dimensions and speed of jet streams?
The jet streams normally are 160–480 km wide by 900–2150 m thick, with core speeds that can exceed 300 km·h−1
When do jet streams tend to be weaker and stronger?
Jet streams in each hemisphere tend to weaken during the hemisphere’s summer and strengthen during its winter as the streams shift closer to the equator.
What is the polar jet stream?
The polar jet stream meanders between 30° and 70° N latitude, at the tropopause along the polar front, at altitudes between 7600 and 10 700 m (Figure 6.14a). The polar jet stream can migrate as far south as Texas, steering colder air masses into North America and influencing surface storm paths travelling eastward. In the summer, the polar jet stream remains at higher latitudes and exerts less influence on midlatitude storms.
What is the subtropical jet stream?
In subtropical latitudes, near the boundary between tropical and midlatitude air, the subtropical jet stream flows near the tropopause. The subtropical jet stream meanders from 20° to 50° latitude and may occur over North America simultaneously with the polar jet stream—sometimes the two will actually merge for brief episodes.
