exam 4

Question 1

Pressure Gradient Force

Answer 1

compels fluid to move from regions of high pressure to regions of low pressure; difference in pressure over distance

Question 2

Coriolis Force

Answer 2

the invisible force that appears to deflect the wind; a direct result of the Earth’s rotation

Question 3

Rotation Rate

Answer 3

of rotations / second

Number of rotations per second

Question 4

Radial Velocity

Answer 4

rotation rate x radius

Question 5

Velocity radial of the Earth

Answer 5

the radial velocity; purely a function of latitude

Question 6

Velocity relative to Earth

Answer 6

possessed anytime an object moves from one location to another

Question 7

Geostrophic Balance

Answer 7

When COR and PGF are equal (friction is negligible)

Question 8

Anti-cyclones

Answer 8

Clockwise in NH, counterclockwise in SH
High pressure zones repel air
Diverge in the surfaces converge aloft

Question 9

Cyclones

Answer 9

Counterclockwise in NH, clockwise in SH
Low pressure zones suck in air
Converge on the surface, diverge aloft

Question 10

Vorticity

Answer 10

a measure of the spin of the air parcel

Question 11

Positive vorticity

Answer 11

getting more counter clockwise

Question 12

negative vorticity

Answer 12

getting more counterclockwise

Question 13

Positive vorticity advection

Answer 13

horizontal transport of positive vorticity; associated with divergence

Question 14

negative vorticity advection

Answer 14

horizontal transport of negative vorticity; associated with convergence

Question 15

Occluded front

Answer 15

The faster cold front overtakes the warm front and pushes the warm front aloft, a signal that the cyclone has reached its peak intensity

Question 16

Warm front

Answer 16

Cold air forces warm air to rise; warm air rises over a shallowly steep parcel of cold air

Question 17

Cold fronts

Answer 17

Steeply sloped cold air forces the warm air to rise

Question 18

A hockey puck is placed on a flat, infinite sheet of ice in the Southern Hemisphere. It is then given a slight push to the west. The sheet of ice is frictionless so that the speed of the puck after the push is constant. What horizontal force acts on the puck after the push? Describe (or draw) the path the puck takes after the push. Explain your description (or drawing).

Answer 18

The force that acts on the puck is the Coriolis force. After the push, the puck will deflect toward the south since it’s in the Southern Hemisphere. The frictionless surface is important because the only forces acting on it are the Coriolis and the push.

Question 19

A friend of yours who is traveling the world reports that she recently experienced a day on which the surface wind blew from the southeast while simultaneously the clouds overhead were moving from east to west. Independently, she is made aware of the fact that on that day the PGF was the same at the surface and at the cloud height. What hemisphere was she in at the time? Explain your answer.

Answer 19

Because the clouds are moving from east to west, she is in the Southern Hemisphere. On the surface, she feels the wind blowing from the southeast because friction has changed the direction of the wind in order to keep the PGF balanced. For winds aloft, friction is negligible, so the wind is in geostrophic balance. Because they’re moving east to west, she is in the Southern Hemisphere.

Question 20

A local forecaster predicts that strong surface winds (i.e. speeds in excess of 15 ms-1) will visit the Upper Midwest over the weekend. Which of the two statements below most likely motivated her forecast?

(a) Small differences in sea-level pressure will exist from station to station across the area.

(b) Large differences in sea-level pressure will exist from station to station across the area.

Give a scientific explanation of your choice.

Answer 20

Statement B will be most likely. The greater pressure differences from station to station will lead to a greater PGF meaning stronger winds because the wind strength is connected with the Coriolis which is dependent on the PGF.

Question 21

What two forces are balanced in geostrophic flow? The winds well above the surface in the middle latitudes are nearly in geostrophic balance. How does this fact serve as proof that the Earth rotates on its axis?

Answer 21

The two balanced forces are pressure gradient force and the Coriolis force. The only forces involved in geostrophic balance are the Coriolis force and the PGF since friction is negligible. Without the COR, the wind would only flow from areas of high pressure to areas of low pressure, which it doesn’t. That means that the COR must be present in the middle latitudes and since COR is only dependent on the rotation of the earth, the earth must be rotating.

Question 22

Thickness of the column

Answer 22

directly proportional to temperature

Question 23

thermal wind/geostrophic wind shear

Answer 23

wind that comes as a result of the pole-to-equator temperature gradient

Question 24

Jet stream

Answer 24

a core of very high-speed winds found very high in the atmosphere

Question 25

air mass thunderstorms

Answer 25

remote from any organized fronts or cyclones

Cumulus stage: growth of the cumulus cloud; warm rising air from which liquid water condenses; no precipitation yet

Mature stage: particles are big enough to start falling, dragging dry air from outside the cloud into it; renders some of the in-cloud air negatively buoyant, helping to develop a significant down draft

Dissipating stage: precipitation ceases from the updraft, cumulus slowly evaporates

Question 26

Severe thunderstorms

Answer 26

Long life span as the result of the tilted updrafts. Downdrafts are restricted to the western portion of the storm. Titled updrafts keep the precipitation from falling into the warm, moist airflow that feeds the storm

Question 27

Tornadoes

Answer 27

In the presence of VWS, tubes of air are made to rotate. The updraft bends/distorts the rotating air sot he rotation becomes more and more vertical (mesocyclones). Air rushes into the mesocyclone, increasing the rotation. The southcentral U.S. is characterized by convective instability: the most potent instability in the atmosphere (dry air on top of moist air)