7.2 Weather Processes

7.2 Weather Processes

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Learning Targets

• I can describe how Earth is heated and how that heat is distributed.

• I can explain the causes of the winds and their direction of movement.

• I can examine the formation of different types of clouds.

• I can explain the formation and accompanying weather conditions of air masses and fronts.

Weather vs Climate

• Weather: The short-term (daily) atmospheric conditions of a location that change very quickly.​

• Climate: The long-term conditions of a location that are constant over many years (20-30 yrs).​

Heat Transfer in the Atmosphere

• The energy that powers our weather system comes from the Sun. It transfer by​

• Radiation - energy that travels in waves

• Conduction – transfer of energy by physical contact

• Convection – transfer of heat by convection currents

Multiple Choice

What do we call the long-term conditions of a location that are constant over many years?

• Climate

• Air pressure

• Weather

• Air masses

Multiple Choice

A scientist is studying energy transfer that occurs in oceans, atmosphere, and Earth’s interior. Which of these is the scientist most likely studying?

• Pressure

• Gravity

• Density

• Convection

Multiple Choice

Which process is primarily responsible for the transfer of energy by air currents within the Earth's atmosphere?

• Convection

• Absorption

• Radiation

• Conduction

Uneven Heating

• Different parts of Earth receive different amount of solar radiation

• Primarily depends on:

  - Seasons (duration of sun light)

  - Latitudes (angle of insolation)

Seasons

• Seasons are caused by a tilt of Earth's axis

• The tilt causes uneven heating of the Earth's surface (hemispheres)

• When the Northern hemisphere is tilted towards the sun, it receives more sunlight/heat than the Southern hemisphere

Latitude and angle of sunlight

• At higher latitudes, Sun's rays hit Earth at an angle, spreading over a larger area (indirect sunlight)

• At equator, Sun's rays hit nearly straight on, and is more concentrated (direct sunlight)

Multiple Choice

When the Northern hemisphere tilts toward the sun, what season occurs in the northern hemisphere

• Winter

• Summer

• Fall

• Spring

Multiple Choice

When the Southern hemisphere tilts toward the sun, what hemisphere receives most direct sun light?

• Southern

• Eastern

• Western

• Northern

Weather Factors

• There are many factors that influence the weather, including, solar radiation, air temperature, air pressure, wind and water vapor in the air (humidity).

• Let's look at each of them....

Weather Factors (Temperatures)

• Unequal heating leads to differences in air temperature.

• When air near the surface is heated, it becomes less dense and rises.

• As the warm air cools, it becomes denser and starts to sink

Weather Factors (Air Pressure)

• When warm air rises, an area of LOW pressure is created

• When cold air sinks causing an area of HIGH pressure is created

• The wind blows from areas of high pressure to areas of low pressure

Multiple Choice

Warm air _________, and cold air__________.​

• rises, rises

• sinks, sinks

• rises, sinks

• sinks, rises

Multiple Choice

Warm rising air leads to a ________ pressure at the Earth's surface, and cold, sinking air leads to a _________ pressure at the Earth's surface.​

• low, low

• high, high

• high, low

• low, high

Multiple Choice

Earth’s surface winds generally blow from regions of ________ air pressure towards regions of __________ air pressure

• lower, lower

• higher, higher

• lower, higher

• higher, lower

Weather Factors (Proximity to Water​)

• Large bodies of water create winds as temperature differs between land and water (land vs. sea breezes).

• Proximity to water also has an impact on the "climate" (continental vs maritime climate)

Weather Factors (Water Vapor)

• "Relative humidity": the % of moisture in the air compared to how much the air can hold at that temperature

• The higher the %, the higher the humidity

• RH changes as the air temperature goes up and down

Multiple Choice

Continental climate has a large temperature difference between summer and winter than maritime climate

• True

• False

Multiple Choice

Warm air can hold less moisture than cold air.

• True

• False

Multiple Choice

What heats up and cools down faster?

• Land

• Water

• They heat up and cool down at the same rate

Relative Humidity & Water Cycle

• When warm air rises, it cools and becomes "saturated" with water vapor

• When RH reaches 100% the water vapor condenses and forms clouds

• Cloud formation often lead to precipitation

Air Masses

• An air mass is a large ”bubble of air” that has similar temperature and humidity​.

• Air masses take on the characteristics of their ”source region”

• There are five air mass classifications: cT, mT, mP, cP, cA

• When two air masses meet, they form a front, which often leads to changes in the weather

Multiple Choice

What comes after evaporation in the water cycle?

• precipitation

• run off

• condensation

• transpiration

Multiple Choice

Compared to a continental polar (cP) air mass, a maritime tropical (mT) air mass is ___________

• cooler and contains more moisture

• cooler and contains less moisture

• warmer and contains less moisture

• warmer and contains more moisture

Multiple Choice

A continental tropical (cT) air mass was formed over a ____________ region

• dry and warm

• dry and cold

• humid and warm

• humid and cold