Cor Knowledge - Wind and Currents

How long do the maximum intensity winds last in an individual microburst?

2-4 minutes

Which condition could be expected if a strong temperature inversion exists near the surface?

A wind shear with the possibility of a sudden loss of airspeed.

Geostrophic wind

A wind that moves parallel to the isobars as a result of the balance between the pressure gradient force and the Coriolis effect.

Katabatic Winds

Also called gravity drainage winds; they are significant on a larger regional scale than mountain-valley breezes, under certain conditions.

What prevents air from flowing directly from high-pressure areas to low-pressure areas?

Coriolis force.

At lower levels of the atmosphere, friction causes the wind to flow across isobars into a low because the friction

Decreases wind speed and Coriolis force

What causes wind?

Differences in air pressure

Downdrafts

Downward rushes of air caused by winds blowing downward, hitting the land and spreading out in strong gusts of wind

Winds at 5,000 feet AGL on a particular flight are southwesterly while most of the surface winds are southerly. This difference in direction is primarily due to

Friction between the wind and the surface

When flying west-east a pilot can expect a tail wind when a ___________ pressure system is south of the craft and a __________ is north of the craft.

High, Low

When may hazardous wind shear be expected?

In areas of low level temperature inversion, frontal zones, and clear air turbulence.

The presence of lenticular clouds is an indication of

Moderate to severe turbulence

What is the expected duration of an individual, microburst?

Seldom longer than 15 minutes from the time of the strike until it dissipates

What causes surface winds to flow across the isobars at an angle rather than parallel to the isobars?

Surface friction

What relationship exists between the winds at 2,000 feet above the surface and the surface winds?

The winds at 2,000 feet tend to parallel the isobars while the surface winds cross the isobars at an angle toward lower pressure and are weaker.

Anabatic Winds

Upslope movements of air, occur in the daytime when the sun can warm a mountain's slopes

The strength and location of the jet stream is normally

Weaker and farther north in the summer.

What is wind?

Wind is the motion of air relative to the surface of the Earth, and is the result of three forces: pressure gradient force, Coriolis force, and surface friction.

Where does wind shear occur?

With either a wind shift or a wind speed gradient at any level in the atmosphere.

The wind system associated with a low-pressure area in the Northern Hemisphere is

a cyclone and is caused by Coriolis force.

Wind shear

a sudden change in wind speed or direction

Updrafts

an upward current or draft of air created by heating of the air near the surface of the earth

The general circulation of air associated with a high-pressure area in the Northern Hemisphere is

outward, downward, and clockwise.