Chapter 10 - Wind: global systems Flashcards
Explain how and why the average surface pressure features shift from summer to winter.
The ITCZ (intertropical convergence zone) moves upwards in summer with the sun and downwards in winter.
Why is it impossible on earth for a Hadley cell to extend from the pole to the equator?
Because of the Coriolis force and rotation of earth.
How does the polar front influence the development of the polar front jet stream?
Low and high pressure areas meet –> polar jet stream (alt 10 km). The polar front is a a cold front with a low pressure area north of it.
Describe how the conservation of angular momentum plays a role in the formation of a jet stream.
Angular momentum is: L = m x v x r
as moving air parcel move closer to the axis –> decrease in radius r –> increase in speed –> angular momentum is conserved –> faster jet streams (at the poles)
List at least four important interactions that exist between the ocean and the atmosphere.
- wind (leads to ocean currents) 2. evaporation 3. ocean currents 4. heat (released from ocean to atmosphere), which helps the general circulation of winds.
How would the general circulation of air appear in summer and winter if earth were tilted on its axis at an angle of 45° instead of 23.5°?
If more tilted, higher seasonality. More extreme weather conditions. Need large circulation pattern since heat diff larger. Incoming heat would change pattern and hence we would need a greater circulation cell to account for the increasing heat diff.
Summer weather in the southwestern section of the United states is influenced by a subtropical high pressure cell, yet fig 12.5b shows an area of low pressure at the surface, explain.
Pacific high moves over sometimes.
Explain why icebergs tend to move at right angles to the direction of the wind.
Since the mass of an iceberg is about 90% beneath and only 10% above the ocean surface, ocean currents are far more important than winds in determining the course of an iceberg. Hence, since the Coriolis force causes the Ekman spiral which in turn causes the average current direction to be at right angles to the direction of the wind (in the clockwise sense as seen from above), the direction taken by an iceberg is also at right angles to the wind.
Explain why the surface water temperature along the northern California coast is warmer in winter than it is in summer.
The prevailing wind along the northern California coast tends to be southward, parallel to the shore, during summer, but nearly onshore, with only a weak north component during winter. Since upwelling is strongest when the wind is parallel to the coast (Ekman spiral at right angles from the wind, cold water replaces the warm), the strongest upwelling and therefore the coolest surface water temperatures occur during the summer.
The Coriolis force deflects the water to the right of its intended path in the Northern hemisphere and to the left in the Southern hemisphere. Why, then, does upwelling tend to occur along the western margin of continents in both hemispheres?
Strong subtropical highs cause prevailing winds to be northerly along the western boundaries of northern continents and southerly along the western boundaries of southern continents. In both cases the Coriolis force (causing a deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere), by means of the Ekman spiral, causes a net westward migration of coastal waters and associated upwelling.
