Transcript Low Clouds

Weather Elements
Summary from Lesson 2
Conduction
 ____________
is the passage of energy, particularly heat and
electricity, through an object. An example is a frying pan
Convection
 ____________
is the process whereby air absorbs heat energy.
Warm air is forced upward as cold air flows displace the warm
air.
 The horizontal transfer of a heat, caused by air movement is
Advection
called ________________.
A good example is fog.
Insolation
 ________________
is the rate at which the Earth’s surface is
heated by solar radiation.
Weather Elements
Know basic facts and general principles of the
elements of weather.
1. Identify types of clouds.
2. Identify types of air masses and fronts.
Overview
1. Clouds
2. Air Masses and Fronts
Types of Clouds
Low Clouds
(300 – 6,500 ft)
 Stratus
• Sheet - like cloud.
• No turbulence.
• May be risen fog.
• Light drizzle or snow.
• Close to Earth’s surface.
• Can hide danger.
Low Clouds
 Stratocumulus
• Rolls or global masses.
• Bulbous protrusions.
• Heavy rain and snow
• Varying turbulence.
• Masks higher severe
cloud buildups.
Low Clouds
 Cumulonimbus
• Vertical growth group.
• Top has anvil shape.
• High winds, snow, hail,
rain, lightning, and
tornadoes.
• Extreme turbulence.
Middle Clouds
(6,500 – 20,000 ft)
 Altostratus
• Relatively thin.
• Sun may be seen
through veil.
• Ice crystals and supercooled water.
• Light precipitation.
• Poor surface visibility.
Middle Clouds
 Altocumulus
• Wavy solid clouds with
rounded outline.
• Light intermittent rain or
snow.
• Commonly followed by
thunderstorms.
• Poor visibility and
moderate surface winds.
High Clouds
(20,000 ft and up)
 Cirrus
• Thin feathery clouds.
• No precipitation.
• Sign of approaching
bad weather.
High Clouds
 Cirrocumulus
• Thin clouds.
• Indicates high-level
instability.
• Similar to cirrostratus but
they have a slightly
“bumpy” appearance.
Fog Types
 Radiation Fog
• Formed at night when
land surfaces radiate
much of the heat
absorbed from the Sun
back into space.
• The cool land surface
cools the air near it to
below the dew point and
fog is formed.
Fog Types
 Advection Fog
• Formed when wind blows
moist air over a cold surface.
• When the surface cools the
air to its dew point
temperature, fog is formed.
Fog Types
 Upslope Fog
• Results when wind
carries moist air up to a
mountain slope or
sloping land.
• The air cools to its dew
point as it rises and
water vapor then
condenses into fog.
Air Mass
 A large body of air (usually extending over an area
1,000 or more miles across) which has generally the
same temperature and moisture content within the
entire mass.
Characteristics of Air Masses
 Cold air masses move more rapidly than warm air
masses.
Fronts
 The boundaries between air masses are called frontal
zones or fronts.
• If a cold air mass replaces a warmer air mass, the
boundary is called a cold front.
• If a warm air mass replaces a cold air mass, the
boundary is called a warm front.
Fronts
 Cold Fronts
• As warm air is forced
upward, it cools,
condenses into clouds,
creating thunderstorms.
• Squall lines develop
ahead of the front.
Fronts
 Warm Fronts
• Front slips upward over cool
air and forms a wedge.
• Rises slowly which delays
condensation.
• As front approaches other
clouds, skies darken.
• Near the frontal boundary,
clouds are low, gentle rain
falls and visibility is poor.
Summary
1. Clouds
2. Air Masses and Fronts