Exam 2 - Weather

Atmospheric pressure

Force exerted by gases per unit area P=F/A

When the area is small _______

Pressure is the highest

Higher the density _____

Higher the pressure

What can also increase pressure?

Temperature

Pressure is proportional to temperature when _____

Volume is fixed

High temperature = _______

Low pressure (thermal low)

Rising warm air = ______

Low pressure (dynamic low)

Low temperature = ______

High pressure (thermal high)

Descending air = _______

High pressure (dynamic high)

Barometer

Measures pressure

What direction does wind move?

Area of high pressure to area of low pressure

Wind is _____

Air in motion (NOT interchangeable)

Updrafts and downdrafts

Small scale movements

Subsidence

Large scale movement of air downwards

Ascent

Large scale movement of air upwards

What is the only force that controls speed?

Gradient (pgf)

What are the three forces that control wind direction?

Gradient, coriolis, frictional

Frictional force ______ with altitude

Decreases

Wind speed _____ with altitude

Increases

Geostrophic air flow

Pressure gradient force and coriolis force are balanced

How does the wind move in geostrophic air flow?

Parallel to the isobars (only in the upper atmosphere)

What is a cyclone?

Air flow in low pressure areas (stormy weather/cloud formation)

What is an anticyclone?

Air flow in high pressure areas (no storms)

Rising air is associated with a/an ____

Cyclone

Sinking air is associated with a/an _____

Anticyclone

What direction does wind flow in the North of a low pressure area?

Counterclockwise

What direction does wind flow in the North of a high pressure area?

Clockwise

What direction does wind flow in the South of a low pressure area?

Clockwise

What direction does wind flow in the South of a high pressure area?

Counterclockwise

A cyclone has what circulation?

Convergent

An anticyclone has what circulation?

Divergent

Wind vane

Measures direction

Anemometer

Measures speed

How do we name winds?

According to where the come from

Prevailing wind

Dominant wind from one direction

What characterizes a sea breeze?

High pressure over water blows to the low pressure land (day)

What is a land breeze?

High pressure over land blows to the low pressure water (night)

What are Chinook winds?

Downslope winds on the leeward side of the mountain

What is another name for Chinook winds?

Santa Ana winds

Where are katabatic winds located?

ONLY on very tall mountains (Mt. Kilamanjaro)

What are Katabatic winds?

Very cold wind on the top of a snow-capped mountain rushing downwards

What is a country breeze?

Cool breeze from the country moving to the warmer city.

Hadley circulation

Warm air rising near the equator and flowing towards the poles

What is the three cell model?

Ferrel cell in midlatitudes, Hadley cell circulation in the tropics, and polar cell

What does ITCZ stand for?

Intertropical Convergence Zone

What is another name for ITCZ.

Doldrums

What are trade winds?

Winds in the tropics

What are the westerlies

Strong winds blowing from the west to the east in midlatitudes

What are the westerlies responsible for?

Bad weather in the south

What are horse latitudes?

2 high-pressure belts that have calm winds and little precipitation often resulting in a dry climate (Sahara desert)

What are polar easterlies?

Dry, cold winds blowing from high pressure poles towards low pressure regions

What are monssons?

Seasonal reversal of wind direction

Characteristice of jet stream

Located inside westerlies up to 300mph, strongest in the winter

El Niño

• Phenomenon associated with excessive flooding

• Close to Christmas time

Where does El Niño occur?

The west coasts of South America

What is an air mass?

Large parcel of air with relatively uniform properties in horizontal dimension moving as an entity

How are air masses characterized?

Based on temperature and moisture of source regions

What is a source region?

Where the air mass orginiates

What are the three categories for masses?

• Polar

• Arctic

• Troipic

What are the two surface areas for masses?

• Maritime

• Continental

Continental polar =

Very cold

Very dry

Maritime polar =

• Cold

• Moist

Continental arctic =

• Extremely cold

• Very dry

Contonental tropical =

• Warm

• Very Dry

Maritime tropical =

• Warm

• Wet

A maritime polar mass changing to a continental polar mass is an example of _____

How air masses can become modified

Warm front

Characteristics of warm fronts

• Cloud type = nimbostratus

• Light precipitation

Cold front

Characteristics of cold fronts

• Cloud type = cumulonimbus

• Heavy precipitation/storms

Stationary front

Occluded front