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
______ the horizontal transport of any atmospheric property by the wind.
advection
There are three (3) forces that control wind speed and direction:
- Pressure-gradient force
- Coriolis force
- Friction force.
_____ is the force that moves air from an area of high pressure to an area of low pressure.
- Pressure gradient force
An instrument used to measure air pressure.
Barometer
A line drawn on a map connecting points of equal pressure. These are quantitative representations of the changing molecular density of the air over a geographic region.
Isobar
The force created by the Earth’s rotation that causes winds to be deflected to the right in the Northern Hemi-sphere and to the left in the Southern Hemisphere
- Coriolis force
force opposing the motion of wind, caused by the drag of the Earth’s surface; greatest close to the surface and decreasing with height.
- Frictional Force
violent or unsteady movement of air or water, or of some other fluid.
Turbulence
River of high-speed air in
the upper atmosphere that
flows along the polar front.
Polar front jet stream
Band of low pressure, calm
winds, and clouds in tropical
latitudes where air converges
from the Southern and Northern Hemispheres.
Intertropical Convergence Zone (ITCZ)
The primary wind system in the tropics that flows toward the Intertropical Convergence Zone on the equatorial side of the Subtropical High-Pressure System.
Trade winds
Band of easterly winds at high latitudes.
Polar easterlies
winds that generally flow from west to east.
Westerlies Midlatitude
Band of high air pressure, calm winds, and clear skies that exists at about 25° to 30° N and S latitude.
Subtropical High (STH) Pressure System
Core of low-pressure zone
associated with the Intertropical Convergence Zone.
Equatorial trough
Zone of high atmospheric pressure at high latitudes.
Polar High
THREE DISTINCT WIND CELLS
Polar cells
Ferrel cell
Hadley cell
The smallest and weakest cells are the _____, which extend from between 60 and 70 degrees north and south, to the poles.
Polar cells
Ferrel cell, Proposed by _______
William Ferrel (1856).
An air flows poleward and eastward near the surface and equatorward and westward at higher altitudes; this movement is the reverse of the airflow in the Hadley cell.
Ferrel cell
A Large-scale convection loop in the tropical latitudes that connects the Intertropical Convergence Zone (ITCZ) and the Subtropical High (STH).
Hadley cell
Hadley cell, Proposed by _______
George Hadley (1735).
High-speed airflow occurring at high levels in narrow bands within the upper-air westerlies and along certain other global latitude zones.
Jet Stream
The swirling air rises and cools, creating clouds and precipitation.
Cyclone
Air comes in from above and sinks to the ground. High pressure centers generally have fair weather.
Anticyclone
An elongated area of elevated air pressure in the upper atmosphere that is typically associated with sunny skies and calm winds.
High-pressure ridge
An elongated area of depressed air pressure in the upper atmosphere that is typically associated with cloudy skies and rain.
Low-pressure trough
A well-organized low-pressure system in the midlatitudes that contains warm and cold fronts.
Midlatitude cyclone
Three (3) types of traveling cyclones.
- The Midlatitude Cyclone
- The Tropical Cyclone
- The Tornado
These cyclones range from weak disturbances to powerful storms.
The Midlatitude Cyclone
A range from mild disturbances to highly destructive hurricanes, or typhoons.
The Tropical Cyclone
A small, intense cyclone of enormously powerful winds.
The Tornado
pileup of water from waves onshore as a severe storm, particularly a tropical cyclone, makes landfall.
Storm Surge
A _______ is any storm that produces thunder and lightning.
Thunderstorms
persist longer than air-mass
thunderstorms and have higher winds. They often
produce hail or even tornadoes.
Severe thunderstorms
is a visible electrical discharge from a cloud.
Lightning
This happens when there is an imbalance of charges between a region of the cloud and another surface (usually the ground, a building, another region of the same cloud, or another cloud) that is significant enough to break through air resistance.
Lightning
any strong, heavy snowstorm with wind.
Blizzard
dust that are carried through the atmosphere by strong winds. Mostly occur in dry, open areas.
Dust storm
also called sandstorm
- Minimal Damage
Winds 33-42 m/s (74-95mph)
Storm Surge 1.2-1.5 m (4-5 ft)
- Moderate Damage
Winds 43-49 m/s (96-110mph)
Storm Surge 1.82-2.4 m (6-8 ft)
(Small trees down, roof damage)
- Extensive Damage
Winds 50-58 m/s (111-130mph)
Storm Surge 2.7-3.6 m (9-12 ft)
(Moderate to heavy damage to home, many trees down)
- Extreme Damage
Winds 59-69 m/s (131-155mph)
Storm Surge 3.9-5.4 m (12-18 ft)
(Severe damage to all structures)
- Catastrophic Damage
Winds > 70 m/s (155mph)
Storm Surge > 5.5m (18 ft)
(Severe damage to all structures)
EF0. Light Damage
39-49 m/s (86-110 mi/hr)
EF1. Moderate Damage
50-60 m/s (111-135 mi/hr)
EF2. Considerable Damage
61-73 m/s (136-165 mi/hr)
EF3. Severe Damage
61-73 m/s (135-165 mi/hr)
EF4. Devastating Damage
74-89 m/s (166-200 mi/hr)
EF5. Incredible Damage
> 90 m/s (>200 mi/hr)
