Weather Unit 6: Humidity and Clouds

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Questions and Answers

What is a large body of air in the troposphere, characterized by similar temperature, pressure, and moisture?

Air mass

What process is the change of liquid water to gaseous water?

Evaporation

What process is the release of water vapor from plants?

Transpiration

Name the factor that describes how much water vapor the air holds, expressed as a percentage.

Relative humidity Signup and view all the answers

At 100% relative humidity, the air is said to be ____.

Saturated Signup and view all the answers

When air cools to its dew point, what happens to the water vapor?

Condensation Signup and view all the answers

What are the four main types of weather fronts?

Cold, warm, stationary, and occluded fronts Signup and view all the answers

What is a front?

The boundary between two different air masses Signup and view all the answers

What is a major source of severe weather events?

Low pressure systems Signup and view all the answers

The strongest storms of tropical origin, with wind speeds exceeding 74 miles per hour, are called ____.

Hurricanes Signup and view all the answers

What are the four conditions required for a hurricane to form?

Humid air, warm ocean water, weak jet stream, extremely low pressure Signup and view all the answers

Tornadoes are the most powerful type of storm.

True Signup and view all the answers

Tornadoes typically form in a funnel shape, rotating around a ____ pressure center.

low Signup and view all the answers

What is the name of the region in the central United States that is particularly prone to tornadoes?

Tornado Alley Signup and view all the answers

How does the Fujita scale classify tornadoes?

Wind speed Signup and view all the answers

What type of storm is characterized by intense snowfall, high winds, low visibility, and below-freezing temperatures?

Blizzard Signup and view all the answers

What type of cloud forms from rising warm air and is associated with thunderstorms, heavy rain, and strong winds?

Cumulonimbus Signup and view all the answers

What is the process by which the warmer air mass is forced upward when a cold front meets a warm front, leading to condensation and precipitation?

Frontal lifting Signup and view all the answers

Match the following types of fronts with their descriptions:

Cold front = A warm air mass moves in on an area of cold air, causing gradual precipitation ahead of the front. Warm front = A cold air mass moves in on an area of warm air, leading to heavy precipitation and rapid temperature changes. Stationary front = A cold front overtakes a warm front, leading to heavier precipitation. Occluded front = Neither air mass is advancing, leading to prolonged precipitation and sluggish weather conditions. Signup and view all the answers

In a station model, the temperature is represented by a number placed ____ of the circle.

above Signup and view all the answers

The dew point temperature is represented by a number placed ____ of the circle in a station model.

below Signup and view all the answers

The wind speed is represented by ____ in a station model.

feather symbols Signup and view all the answers

The wind direction is represented by a ____ in a station model.

barbed arrow Signup and view all the answers

What is the name of the region in the atmosphere where condensation nuclei, such as dust particles and aerosols, play a crucial role in cloud formation?

Troposphere Signup and view all the answers

What is the name of the process by which water vapor changes back into liquid water in the atmosphere?

Condensation Signup and view all the answers

What is the name of the process by which warm, moist air rises, cools, and condenses to form clouds and precipitation?

R.E.C.C Signup and view all the answers

What is the name of the instrument used to measure liquid precipitation?

Rain gauge Signup and view all the answers

What is the basic definition of precipitation?

The falling of liquid or solid water from clouds towards Earth's surface Signup and view all the answers

What types of weather fronts are associated with the rapid development of thunderstorms?

Cold fronts Signup and view all the answers

Hurricanes weaken when they travel over land or cool water.

True Signup and view all the answers

What are the main components of a hurricane?

Eyewall, eye, and rain bands Signup and view all the answers

The ____ of a hurricane is the calmest area at its center, with little to no winds.

eye Signup and view all the answers

The area surrounding a hurricane's eye, characterized by the strongest winds and heaviest rainfall, is called the ____.

eyewall Signup and view all the answers

What is the name of the scale used to classify the intensity of hurricanes based on their wind speeds?

Saffir-Simpson Hurricane Wind Scale Signup and view all the answers

Study Notes

Unit 6 - Weather, Part 2

This unit covers relative humidity, clouds, air masses, fronts, and severe weather.

Atmospheric Moisture

Water vapor is gaseous water in the atmosphere.
Water enters the atmosphere through evaporation (liquid to gas) and transpiration (plants releasing water vapor).

Net Evaporation Rate Factors

Insolation: Higher insolation provides more energy for evaporation.
Surface Area: Increased surface area leads to a greater evaporation rate.
Humidity: Drier air results in faster evaporation.
Wind Speed: Increased wind speed accelerates evaporation

Humidity

Relative humidity expresses how "full" the air is with water, expressed as a percentage.
Hotter air can hold more water vapor than colder air (due to expansion).
If the air temperature changes but the water vapor amount stays the same, the relative humidity changes.

Temperature vs. Relative Humidity

As air temperature increases, its ability to hold water vapor increases.
If the air temperature of a parcel increases, and the amount of water vapor stays the same, the relative humidity decreases.

Dew Point

Dew point is the air temperature when the air is full to capacity with water vapor (100% relative humidity).
At 100% relative humidity, the air is saturated.
When the air is saturated, some water vapor begins to condense (gas to liquid).
Relative humidity increases as the air temperature gets closer to the dew point temperature, and the chance of precipitation also increases.

Measuring Moisture - Sling Psychrometer

Sling psychrometers measure relative humidity and dew point using wet-bulb and dry-bulb thermometer readings.
The wet-bulb temperature is always less than or equal to the dry-bulb temperature.

Determining Relative Humidity and Dew Point

Use the reference tables (ESRT) provided to determine relative humidity and dew point.

Cloud Formation (R.E.C.C.)

As air heats at the surface, it rises and expands.
As air cools it contracts and reaches its dew point temperature.
Water begins to condense or change from a gas to a liquid.
Water droplets form on condensation nuclei (dust particles or aerosols in the air).

Precipitation

Precipitation is the falling of liquid or solid water from clouds towards Earth's surface.
The solid/liquid particles collide until they are heavy enough to fall under the influence of gravity.
Types of precipitation include rain, drizzle, snow, sleet, freezing rain, and hail.

Measuring Precipitation

A rain gauge measures liquid precipitation in depth (usually in inches or centimeters).

Air Masses

Air masses are large bodies of air in the troposphere with similar characteristics throughout (pressure, moisture, and temperature).
Air masses form when air remains stationary over an area, adopting the characteristics of its source region.

Characteristics of Air Masses

Moisture Level: Land/Continental areas form dry air masses; Ocean/Maritime regions form wet air masses.
Temperature: Polar regions create cold air masses; Tropical regions create warm air masses.

Air Mass Symbols

Reference tables (Page 13) provide symbols for cA (continental arctic), cP (continental polar), cT (continental tropical), mP (maritime polar), and mT (maritime tropical) air masses.

Jet Streams & Planetary Winds

Jet streams and planetary winds move air masses around the globe, influencing storm paths across the U.S.

Weather Fronts

Weather fronts are boundaries between different air masses with contrasting densities.
Four types of fronts include cold fronts, warm fronts, occluded fronts, and stationary fronts.
Cold front: Boundary where a cold air mass moves into a warm air mass. Rapidly pushes warm air aloft; thunderstorms are common.
Warm front: Boundary where a warm air mass moves into a cool air mass; warm air rises over cool air, leading to widespread rain.
Occluded front: Warm air gets trapped between two cold fronts.
Stationary front: Air masses push against each other but neither moves.

Precipitation & Fronts

Cold fronts bring precipitation at the frontal boundary.
Warm fronts often bring precipitation well ahead of the front.

Severe/Extreme Weather

Storms are violent or severe atmosphere disturbances causing dangerous or destructive conditions on Earth's surface.
Examples include hurricanes, thunderstorms, tornadoes, hail, and blizzards.

Mid-Latitude Cyclone Storms

Severe weather events with precipitation are low-pressure storm systems, where winds move counterclockwise and inward. Air rises from Earth's surface into the atmosphere, following R.E.C.C. (rising, expanding, cooling, and condensing).

Hurricanes

Hurricanes are strong storms of tropical origin with sustained winds exceeding 74 mph.
For a hurricane to form, four conditions are needed: humid air, warm ocean water, a weak jet stream, and extremely low pressure.
Hurricanes gain energy from warm tropical ocean waters, and they typically form in late summer or early fall because of temperature lag.
Hurricanes commonly originate off the coast of West Africa, and are pushed westward by planetary winds, then northeastward by southwesterlies.
Hurricanes lose strength when they travel over land or cool water.

Saffir-Simpson Scale

The Saffir-Simpson Scale categorizes hurricanes based on wind speed and resulting damage (1-5).

Preparing for a Hurricane

Prepare an escape route.
Tape/board up windows.
Stock up on food, water, and candles.
Move to higher ground.

Thunderstorms

Thunderstorms are heavy rain storms accompanied by thunder and lightning.
They form from rising warm air associated with fronts (and hurricanes, as part of their cycle), featuring cumulonimbus clouds (anvil clouds).
Hazards include flooding, hail, high winds, and lightning.

Tornadoes

Tornadoes are low-pressure funnel clouds that extend down towards the Earth's surface.
Most tornadoes only last a few minutes.
They are the most violent of storms.
Tornado Alley is the most prone area in the U.S. for tornadoes, where mT air from the South meets cP air from the North.

Fujita Scale

The Fujita Scale categorizes tornadoes based on wind speed and damage.

Blizzards

Blizzards are intense winter storms with heavy snowfall, high wind speeds, low visibility, and below-freezing temperatures.
To prepare: Stock up on supplies (food, water, batteries, blankets) and stay inside or off the road.

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Description

Explore the key concepts of atmospheric moisture, relative humidity, and cloud formation in this quiz. Understand how factors like temperature, insolation, and wind speed influence evaporation and humidity levels. Test your knowledge on severe weather and the behavior of air masses and fronts.