Chapter 12 -- Notes Flashcards
Does warm air decrease more gradually in pressure with altitude than cold air?
Yes. Because the cold air is more dense. Consequencly at the same altitude above Earth’s surface, higher pressure exists over the tropics and lower pressure is the norm over the poles.. Thus, the resulting pressure gradient is directed from the equator toward the poles.
What is a Jet stream?
Embedded within the westerly flow aloft are narrow ribbons of high-speed winds that meander for thousands of kilometers. These fast streams of air are called Jet streams.
What is the Polar jet stream?
The best-known jet stream.
Occurs along a major frontal zone called the polar front.
Moves northward during summer and southward in winter.
Travels faster in winter and slower in summer.
As the polar jet shifts northward, there is a corrosponding change in the region where outbreaks of severe thunderstorms and tornadoes occur.
What is the Subtropical jet stream?
A semipermanent jet that exists over the subtropics. The subtropical jet is mainly a winter phenomenon. Due to the weak summertime temperature gradient, the subtropical jet is relatively weak during the warm season.
What are Rossby waves?
Waves in jet streams path that are 4000 to 6000 kilometers.
In addition to Rossby waves, shorter waves occur in the middle and upper troposphere. These shorter waves are often associated with cyclones at the surface and they travel from west to east around the glove at rates of up to 15* of longitude a day.
What regions experience dry conditions?
What regions recieve ample precipitation?
Generally, regions influenced by high pressure, with its associated subsidence and divergent winds, experiance dry conditions. Large landmasses in the middle latitudes commonly experience decreased precipitation toward their interiors. Leeward slopes and adjacent lowlands are usually deficient in moisture.
Regions under the influence of low pressure and its converging winds and ascending air. Windward mountain slopes receive abundant precipitation.
What is the Zonal distribution of precipitation that we would expect on a uniform Earth?
- Equatorial low - ITCZ
- Abundant precipitation in all seasons.
- Equatorward of Subtropical high
- Summer wet, winter dry
- Subtropical High
- Dry in all seasons
- Poleward of Subtropical High
- Winter wet, Summer dry
- Supbolar low
- Ample precipitation in all seasons
- Polar high
- Sparse precipitation in all seasons
Why do eastern regions of subtropical contintents generally receive more precipitation than the western regions?
Because of the different characteristics of the subtropical high-pressure centers that dominat the circulation in these latitudes. Subsidence is most pronounced on the eastern side of these oceanic highs, and a strong temperature inversion is encountered very near the surface and results in stable atmospheric conditions. The upwelling of cold water along the west coasts of the adjacent continents coolds the air from below and adds the the stability on the eastern sides of these highs.
On the western side of these highs, however, subsidence is less pro
