Earth Science Test 11

Weather

Weather

The conditions of the atmosphere at a particular time and place

Meteorologist

A scientist who studies weather

Air Temperature

A measure of the average speed of air molecules

Air or Atmospheric Pressure

The push or force of the air on Earth’s surface

Relative Humidity

The amount of water vapor in the air compared to the maximum possible

Dew Point

Air temperature at which water vapor condenses into dew, frost or clouds

What happens when the air temp and dew point are close?

When the air temp and dew point are close there is going to be high humidity.

Wind Velocity

The speed and direction of air moving across the ground

What makes wind?

Wind is made by the air moving from high air pressure to low pressure areas.

Isobars

Lines on a weather map used to show air pressure and wind

How are isobars on a weather map helpful?

Isobars are helpful because when the lines are close together it means that there is very strong winds.

How are evaporation and condensation an important part of weather?

Evaporation is going to cause humidity in the air and condensation will cause cloud formation.

Precipitation

Any type of liquid or solid water that falls to Earth’s surface

Rain

Precipitation made when water droplets or ice crystals melt and fall

Freezing Rain

Raindrops that freeze when they hit the ground

Sleet

Small ice pellets made when rain freezes before hitting the ground

Hail

Lumps of ice that fall from thunderstorm clouds

Air Mass

A body of air with similar air pressure, temperature, and humidity

What causes and air mass to form?

An air mass is formed when a large area of air sits over a region of the Earth, for many days it will take on the characteristics of the land and water below forming an air mass.

How do air masses move across the U.S.?

Air masses move across the U.S. by a jet stream that pushes air from West to East across the U.S.

Continental Tropical

Warm and dry air mass

Continental Poler

Cold and dry air mass

Maritime Tropical

Warm and humid air mass

Maritime Poler

Cold and humid air mass

High Pressure System

Air moving clockwise around dense, sinking air

Low Pressure System

Air moving counterclockwise around less dense, rising air

Why do low pressure systems cause stormy weather?

Low pressure systems allow the water vapor in the air to rise high enough to cool and condense into clouds.

Front

A transition zone or boundary between 2 air masses

Cold Fronts

When a cold air mass pushes warmer air across the land causing colder temperatures, short bursts of heavy precipitation and or / thunderstorms, fast moving

Warm Fronts

When a warm air mass pushes colder air across the land causing thick, low clouds and widespread light precipitation with warmer temperatures, slow moving

Stationary Front

When equal powered cold and warm air masses temporarily stop moving causing unpredictable conditions depending on whether the warm front or cold front is overhead

Occluded Front

When 2 cold air masses meet as they push a warm air mass higher in the atmosphere causing long, gentle rains followed by short, heavy rains and / or thunderstorms

What causes clouds and precipitation?

Evaporation causes water vapor to rise into the atmosphere, rising water vapor cools to dew point making clouds of water drops or ice crystals, and when these drops or crystals grow large and heavy, gravity pulls them down as precipitation.

Fog

A cloud whose base is at ground level

Cirrus

Feathery or wispy white clouds that form in very cold air above 18,000 feet resulting in no precipitation

Stratus

Flat gray layers of cloud found below 6,000 feet that cause drizzle, freezing rain and / or snow

Cumulus

Puffy white clouds with a darker base found below 6,000 feet that rarely cause precipitation

Cumulonimbus

Very large, tall, dark bottomed clouds can reach up to 60,000 feet, they can produce heavy thunderstorms and heavy rain, hail or snow

What causes different types of clouds at different heights?

The difference between the air temperature and the dew point is smaller, clouds form at lower altitudes. When the spread is larger, clouds form at higher altitudes.

How do you calculate the height at which clouds form?

1. You subtract the dew point from the air temperature

2. Divine by 4.4

3. Multiply by 1,000

   1. Add your total to the elevation of the location

Thunderstorms

A well developed cumulonimbus clouds made of warm, humid air

Tornado

A spiral column of fast - moving wind that lowers from cumulonimbus cloud to land

Tropical Storm

A large, low pressure thunderstorm with wind speeds faster then 38 miles per hour

Hurricane

A very large, spiral, low pressure thunderstorm which forms over the Atlantic Ocean with wind speed over 74 miles per hour accompanied by wind, rain, thunder, lightning, hail, and flooding

Typhoon

A hurricane that forms over the Pacific Ocean

Storm Surge

A dome of water pushed onto land during storms such as hurricanes

Lake Effect

Wind moving across a lake picks up moisture which cools and condense at the shore causing heavy snowfall

Bomb Cyclone

A low pressure storm system that undergoes rapid intensification resulting in strong winds and heavy precipitation

Atmospheric River

A long, narrow weather system over water carrying massive amounts of water vapor falls as rain and snow when they make landfall