1.2 - WEATHER SYSTEMS Flashcards
Physical state of the atmosphere at a given time and place.
Weather
It involves such atmospheric phenomena as temperature, humidity, precipitation (type and amount), air pressure, wind, and cloud cover.
Weather
simply the movement of warm and cold air across the globe. These movements are known as low-pressure systems and high-pressure systems.
Weather systems
Low, thick clouds tend to ____ the Earth
cool
high, thin clouds tend to ____ it
warm
large bodies of air with fairly uniform temperature and moisture characteristics.
Air Masses
Air masses acquire their characteristics in _____
source regions
an extensive region of the earth’s surface where large masses of air having uniform temperature and humidity conditions characteristic of the region originate.
Source Region
In a source region, ____ or not at all, which allows the air to acquire temperature and moisture characteristics from the region’s land or ocean surface.
air moves slowly
This form when large bodies of air acquire the temperature and moisture characteristics of the underlying surface.
Air Masses
Two Surface Types
Maritime air masses
Continental air masses
form over water and are humid.
Maritime air masses
form over land and are dry.
Continental air masses
Air masses is classified by:
latitude zone (arctic, polar, tropical, equatorial)
surface type (maritime, continental)
The classification system for air masses uses a _____ abbreviation.
two-letter
The first letter is lowercase and signifies the _______ characteristics.
The second letter is uppercase and refers to the ________ characteristics.
moisture
temperature
The first letter is lowercase and signifies the moisture characteristics, where:
“c” is for ______
“m” is for _____
continental (dry)
“maritime” (humid)
The second letter is uppercase and refers to the temperature characteristics:
“A” for _________
“P” for _________
“T’” for _________
“E” for _________
Arctic (or Antarctic)
Polar (somewhat warmer than Arctic)
Tropical
Equatorial
An “A” air mass is inherently ______, because water in such areas is often frozen.
continental (dry)
An “E” air mass is inherently _______, because so much of the air at equatorial latitudes is over or near a source of water
maritime
surface of contact between two unlike air masses.
Front
TYPES OF FRONTS
cold front.
warm front.
stationary front.
occluded front.
dry line.
This front is typically associated with intense rain of short duration.
When cold air invades warmer air, the boundary is a
cold front
This front is typically associated with slow, steady precipitation.
When warm air invades colder air, the boundary is a
warm front
develops when warm air and cold air meet and the boundary between the two does not move
stationary front
When a cold front overtakes a warm front, the new front is called an
occluded front
“Occluded” means closed or shut off
A final type of front—called a
dry line
air motion, dominantly horizontal relative to the Earth’s surface.
Wind
Atmospheric Pressure Systems
High-pressure system
Low-pressure system
High-pressure systems keep moisture from rising into the atmosphere and forming clouds. Therefore, they are usually associated with _____
clear skies.
Low-pressure system are rotating masses of warm, moist air. They usually bring ______
storms and high winds.
The _____ of horizontal winds causes air to rise
convergence
The _____ of horizontal winds causes downward motion of the air
divergence