Block II - Set #2

T/F - Most precipitation in the middle and high latitudes begins as rain

FALSE

Frost

Deposition product

Frostpoint

Temperature and dewpoint are below freezing temperature

White Dew

Condensation product that subsequently freezes

Dew

Condensation product

Sensible heat

Measurable when water molecules go to a lower energy state

T/F - If you see a cloud the air is saturated

TRUE

In order to saturate the air for the water vapor to condense on particulates

You can cool the air by adiabatic expansion

You can cool the air by coming into contact with a colder surface

T/F - The dewpoint temperature is always less than the air temperature

TRUE

What corresponds to high pressure areas within the general circulation?

Horse Latitudes

Diverging Winds

30* north (and south) latitudes

What causes the two circulation cells of the general circulation to have north easterly surface winds in the Northern Hemisphere?

Coriolis Force

Which of the following cause the two circulation cells of the general circulation to break up into three circulation cells (per hemisphere, north and south)?

Daily rotation of the Earth

Polar Cell

60 degrees north latitude to north pole

Hadley Cell

Equator to 30 degrees north latitude

Ferrel Cell

30 degrees north latitude to 60 degrees north latitude

Intertropical Convergence Zone (ITCZ)

Low pressure area near the equator, caused by trade winds flowing into each other.

Also called the doldrums

Horse Latitudes

High pressure area near 30 degrees north latitude; cloud formation is suppressed and precipitation is generally low

What causes the monsoon circulation?

Land-sea differences

Order the size of circulations from smallest to largest:

Thunderstorm, Cumulus, Front, Land/Sea Breeze

Smallest

• Cumulus

• Thunderstorm

• Land/sea breeze

• Front

Largest

The global circulation is a combination of

The monsoon circulation

The general circulation

On the real earth ______________ is embedded in the larger general circulation

On the real earth the monsoon circulation is embedded in the larger general circulation

The motion in a given circulation or eddy may be

horizontal and/or vertical

The polar front is a location of __________________ winds and a _______________ area

The polar front is a location of converging winds and a low pressure area

The subtropical high pressure front located at 30 degrees north latitude has _________________ winds and is called ___________________

The subtropical high pressure front located at 30 degrees north latitude has diverging winds and is called horse latitudes

Order the scales of circulations from largest to smallest:

Macroscale microscale mesoscale

Largest

• Macroscale

• Mesoscale

• Microscale

Smallest

T/F - On the real earth the general circulation is embedded in the larger monsoon circulation

FALSE

The larger monsoon circulation is embedded in the general circulation

T/F - Does the location of the Intertropical Convergence Zone move to a lower latitude in the winter

TRUE

Scales of circulations refers to

Sizes and lifetimes of individual circulations

The frontal position aloft

Is always on the colder side

Extratropical Cyclones

Move from west to east

Embedded in the prevailing westerly winds

Incipient Stage

Local stationary front is present; cold airmass to the north and warm airmass to the south.

The actual cyclone development begins when pressure falls at some point along the original front (usually the stationary front)

The incipient stage is also called the Wave Cyclone stage because the stationary front is distored into a wave shape

Occluded Stage

When the cold airmass trailing the cyclone is swept around the low and overtakes the retreating cold air ahead of the cyclone, pushing the warm sector air aloft

The cyclone slows down appreciably

Dissipating Stage

Marked by an increase in the central pressure of a low-pressure system

Downdrafts spread throughout the lower levels of the cell cutting off its energy sources (heat and moisture)

Deepening Stage

Central pressure of wave cyclone continues to drop and wind speeds increase

The Polar Front Model is used

To explain the formation of an extratropical cyclone and has both an upper-air and surface component. 

T/F - All extratropical cyclones develop beyond the wave cyclone stage

FALSE

Sometimes the low pressure system just dissipates along the polar front (pressure increases)

(During the incipient or wave cyclone stage) If the extratropical cyclone continues to develop what happens?

The entire low pressure system moves NE at 12-25kts

Its direction of movement will parallel the surface isobars in the warm sector

During the deepening stage of an extratropical cyclone, winds

Speed up

Cyclonic flow in the northern hemisphere is characterized by

Low Pressure

Counter clockwise rotation

What is mP, mT, cP, cT

Airmasses are classified by there temperature and moisture (this depends on where they come from on Earth)

mP - moist cool air mass

mT - moist warm air mass

cP - dry cool air mass

cT - dry warm air mass

An airmass is modified depending upon the speed at which it moves away from its source region. If it moves _____________, there is _______________ change. 

An airmass is modified depending upon the speed at which it moves away from its source region. If it moves fast, there is little change. 

The opposite is also true. If it moves slow there is a lot of change

Airmass

Extensive body of air within which the conditions of temperature, stability and moisture are uniform

Cyclogenesis

Development or strengthening of cyclonic circulation in the atmosphere

Cold airmass

Airmass that is colder than the ground over which it is moving

The steeper the frontal slope

The greater the amount of frontal lifting

One of the easiest ways of recognizing a front on a map is to note a change in 

Temperature

An extratropical cyclone is also called a

Frontal low

Frontal cyclones

What initially causes frontal lows (extratropical cyclones) to develop?

Locally strong temperature gradients can cause frontal lows (extratropical cyclones) to develop

This is common in the winter along the Gulf of Mexico/East Coast due to the warm ocean next to the cold land

Pre-Development stage

For the extratropical cyclone to form:

The most common case is that there is a local stationary front

Cold air mass to the north, warm air mass to the south

The frontal position aloft

Will be different than its surface position

Will always be on the cold air side of the frontal position at the surface

Fronts are defined according to which airmass

Is advancing

What are the characteristics of an approaching warm front?

Steady precipitation

Stratiform clouds

What are the characteristics of a cold front?

When air is moist and unstable, cumuliform clouds and showers

What is a cold front occlusion?

Air ahead of warm front is warmer than air behind the overtaking cold front

What is overrunning?

When a warm moist airmass moves over a cooler airmass

Boundary of this is marked by a warm front or a stationary front

The weather associated with this is low clouds, poor visibility and freezing precipitation

A cyclone is always stronger aloft _______

than at the surface (as measured by wind speeds)

If you are flying in the Northern Hemisphere and you are experiencing a continuous left crosswind which is associated with a major wind system

You are flying toward a low pressure area

There are likely unfavorable weather conditions ahead

What are the four types of fronts?

Cold Front - Cold air mass is advancing

Warm Front - Warm air mass is advancing

Stationary Front - Neither front is moving (cold front and warm front sit next to eachother)

Occluded Front - Cold front overtakes warm front

Frontal lifting

Lifting of moist air when air masses meet

If there is sufficient moisture present clouds and precipitation will form

What is an extratropical cyclone?

A macroscale low pressure disturbance that develops outside the tropics in the vicinity of the polar front

What is a frontal zone?

A narrow transition region between two air masses. It is not a thin line it may be 1/2NM to 100NM across

Always has rapidly changing conditions across it

Often the location of strong windshear and turbulence

If a cold front is to your left and a warm front is to your right and you are flying from right to left, when will you encounter the frontal zone?

If you are flying from right to left you will encounter the frontal zone later than what you see on the surface chart

If you are flying from left to right you will encounter the frontal zone sooner than what you see on the surface chart

What is the correct order of frontal cyclone development?

1 - Pre-development

2 - Incipient

3 - Deepening

4 - Occluded

5 - Dissipating

What is filling?

An increase in the central pressure of a low pressure system

Filling marks the beginning of the dissipating stage (the end) of an extratropical cyclone

What does the pressure during frontal passage?

Front approaches = pressure drops

Front passes = pressure rises

The sharp change in pressure gradient across a front corresponds to a sharp wind shift (wind shear)

Where upward motions occur surronding a cyclone

Cloudiness and precipitation is produced