Air Masses
What is an air mass?
An air mass is a large body of air that has fairly uniform temperature and humidity.
What is a thunderstorm? List two basic ingredients needed for thunderstorms to form.
A thunderstorm is a storm with thunder and lightning. Two basic ingredients: moisture and unstable air (plus a lifting mechanism like a front or surface heating).
What is evaporation?
Evaporation is the process where liquid water turns into water vapor and enters the atmosphere.
What is atmospheric (air) pressure?
Atmospheric pressure is the force per unit area exerted by the weight of the air above a point.
Name the layer of the atmosphere where most weather occurs.
The troposphere.
How are air masses named? Give the two parts typically used in the name.
They are named by moisture source maritime and continental and temperature tropical and polar
How does hail form during a thunderstorm?
Hail forms when strong updrafts carry raindrops upward into very cold parts of the storm where they freeze; repeated cycles of being carried up and falling allow layers of ice to build until the hailstone becomes heavy enough to fall to the ground.
What is transpiration and how does it add water vapor to the atmosphere?
Transpiration is the process by which plants release water vapor through tiny pores (stomata) in their leaves; together with evaporation from surfaces, transpiration adds water vapor to the air and contributes to atmospheric moisture.
How does air pressure generally change as elevation increases?
Air pressure decreases as elevation increases.
What instrument do meteorologists use to measure atmospheric pressure, and how can its readings help forecast weather?
Meteorologists use a barometer to measure atmospheric pressure; rising pressure often indicates improving, clearer weather, while falling pressure usually signals an approaching low‑pressure system and possible clouds or storms.
Describe one way a continental polar air mass affects weather when it moves over a region.
the air mass brings cold, dry conditions; it can lower temperatures and reduce humidity and may cause clear skies or lake‑effect snow if it passes over a warm lake.
Describe the main difference between a hurricane and a tornado in terms of size and duration.
Hurricanes are much larger (hundreds of kilometers) and can last days to weeks; tornadoes are much smaller (hundreds of meters to a few kilometers) and typically last minutes to hours.
Define relative humidity in a single sentence.
Relative humidity is the percentage of water vapor present in the air compared to the maximum amount the air could hold at that temperature
A falling barometer often indicates what change in the weather—improving, worsening, or staying the same? Explain.
Worsening weather—falling pressure usually signals an approaching low‑pressure system and likely clouds, precipitation, or storms.
Explain how satellite images help meteorologists predict large‑scale weather patterns.
Satellites show cloud patterns, storm locations, and moisture/temperature textures across wide areas, allowing forecasters to track storm movement, fronts, and jet stream behavior.
Explain why a maritime tropical air mass often brings humid conditions.
Because it forms over warm oceans, it contains a lot of evaporated water vapor, making the air warm and humid.
What causes flash floods to occur rapidly in some storms? Provide two contributing factors.
Intense heavy rainfall and saturated or impermeable ground. Steep terrain or poor drainage also speeds runoff, causing rapid flooding
Explain how dew point helps meteorologists predict fog or dew formation.
Dew point is the temperature at which air becomes saturated; if the air cools to its dew point near the surface, dew or fog is likely to form.
Describe how a low‑pressure system affects air movement and typical weather near its center.
In a low, air converges at the surface and rises; rising air cools, forming clouds and precipitation—low centers are often cloudy and stormy.
Define "front" and list the four main types of fronts.
A front is a boundary between two different air masses. The four main types are cold front, warm front, stationary front, and occluded front.
When a cold, dry air mass collides with a warm, moist air mass, what large‑scale weather feature commonly forms along their boundary? Name and briefly describe it.
A front (such as a cold front or warm front) forms; along the boundary, warmer air is forced to rise, often creating clouds and precipitation—cold fronts often cause stronger storms.
Explain how wind shear can contribute to severe thunderstorms becoming more organized and potentially producing tornadoes.
Wind shear (change in wind speed/direction with height) tilts and separates updrafts from downdrafts, allowing storms to stay strong longer and enabling rotation in the updraft that can lead to tornado formation.
Describe the process of how a cloud droplet grows into a raindrop
In warm clouds, small droplets collide and merge (collision–coalescence) to form larger raindrops; in colder clouds, ice‑crystal processes
Explain why strong pressure gradients lead to higher wind speeds. (Use the idea of pressure difference and force.)
A strong pressure gradient means a large pressure change over a short distance, creating a greater pressure‑force per unit area that accelerates air more, producing stronger winds.
Describe how human activities can influence local atmospheric conditions give two examples
Examples: urban heat islands make cities warmer due to heat‑absorbing surfaces and buildings; air pollution can change cloud formation (acting as cloud condensation nuclei) and reduce air quality; deforestation can alter local humidity and rainfall patterns.