Chapter 12 - Middle-latitude cyclones Flashcards
Why do mid-latitude cyclones usually die out after they become occluded?
The supply of warm air is cut off and cold, dry air is drawn towards the surface low. Additionally the surface low pressure move out from the region of upper-level divergence.
Explain this fact: Without upper-level divergence, a surface open wave would probably persist for less than a day?
air spirals into surface low because of friction so unless divergence exists above the low it fills in quickly.
Why do middle-latitude surface low-pressure areas tilt westward with increasing height?
Because of the temperature gradient between the cold air from the north and the warm air from the south.
How are longwaves in the upper-level westerlies different from shortwaves?
Longwave = stationary and slower. Long distance between throughs and ridges. Go eastward and westward sometimes.
Short waves = small disturbences, faster than the longwave. Short distance between throughs and ridges. Go eastward.
How does the polar-front jet stream influence the formation of a mid-latitude cyclone?
Creates areas of high and low pressure. See image page 341. Divergence in the polar jet stream makes the air rise and creates low pressure area.
Explain why, even though the polar-front jet stream coincides with the polar front, some surface regions are more favorable for the development of mid-latitude cyclones than others.
Mountain ranges. Also because the polar jet stream is strongest and moves farthest south in the winter while if shifts northward in the summer, pulling mid-latitude cyclonic storms with it
What are the sources of energy for a developing middle-latitude cyclone?
Warm air rising. Potential energy converted to kinetic energy through latent heat when condensing. Mostly the temperature gradient.
Explain why, at 500 millibars, when cold advection is occurring, the air temperature does not drop as fast as it should.
When the cold air replaces the warm air it also heats up because it is in a stable environment. It heats up while it sinks.
Over earth as a whole, would you expect the atmosphere to be mainly barotropic or baroclinic?
Barotropic.
Baroclinic waves seldom form in the tropics. Why?
Not a lot of temperature and therefore pressure changes.
If polar lows form in frigid polar air over water, how is the atmosphere made conditionally unstable so that towering convective cumulus clouds can form?
water is warmer and heats the surface air that creates the cumulus clouds.
