WEATHER AND CLIMATE

Chapter 28

I. EARTH’S ATMOSPHERE – 2.8A. Composition of Earth’s Atmosphere

1. The atmosphere today a. What are the three major gases found in our Atmosphere?

1. Nitrogen:78% 2. Oxygen:21% 3. Argon: 1%

b. What are the trace gases found in our atmosphere?1. Water vapor2. Argon3. Carbon dioxide4. Ozone5. Neon6. Methane

7. Nitrogen oxides

2. Life and the atmospherea. When is carbon dioxide the least found in our atmosphere? In the Northern Hemisphere because of increased photosynthetic

activity in the Spring and Summer months, October has the minimum amount of CO2.

b. When is carbon dioxide the most in our atmosphere?In the fall and winter, photosynthetic activity decreases andcarbon dioxide reaches its maximum amount in May.

B. Structure of Earth’s Atmosphere 1. Please Define Troposphere: Lowest layer of the atmosphere, extending 12

km above Earth’s surface, layer where weather takes place.

2. Please Define Temperature Inversion:Describes the increasing temperature of air with increasing altitude.

3. The stratospherea. Please Define Stratosphere:

Above the troposphere and includes the ozone layer where the temperature always increases with altitude.

b. Please Define Tropopause:Place in the Stratosphere where temperature inversion begins. This increase of temperature is caused by the ozone layer absorbing ultraviolet radiation from the Sun.

c. Please Define Mesosphere:Layer of air above the Stratosphere wheretemperature of the air decreases.

d. Please Define Thermosphere:Layer above the Mesophere where the temperature of this air layer increases.

e. Please Define Exosphere:The air layer above the Thermosphere in which the temperature of the air increases. This is also our highest or furthest away from the Earth air layer.

C. Heating the Atmosphere1. How much energy is reflected back into

space by our atmosphere? About 30% of the Sun’s radiant energy is reflected back into space because of our reflective atmosphere, clouds, and the water or ice surfaces of our planet.

2. How much radiant energy is absorbed by our atmosphere?Twenty percent is absorbed by the atmosphere especially in the ozone layer within the Stratosphere where there is an increase in temperature.

3. Please Define Greenhouse Effect:Natural process in which certain gases in the atmosphere absorb and emit infrared radiation, warming the planet.

4. What other processes help heat up our Atmosphere?a. Convection of heat transfers thermal energy as warm air masses.

b. Also, the release of latent heat warms the atmosphere by releasing heat when water changes state from a gas to a liquid (condensation) or from a liquid to solid (freezing).

D. Heat Absorption by Earth Surfaces1. What causes the changes in the Weather?

Remember about 50% or the Sun’s radiation reaches and is absorbed by the Earth’s surface. The uneven heating of the Earth’s surface causes the changes in the Weather.

E. Water in the Atmosphere 1. Types of clouds

a. Please Define Stratus clouds: Stratus clouds are layered, sheetlike clouds

that form at altitudes below 2,000 m or 2 km. Stratus clouds are often associated with rain.

b. Please Define Cumulus clouds: Cumulus clouds are puffy in shape and often occur with fair

weather. Cumulus clouds are typically below 2,000 m or 2 km.

b. Please Define Cirrus clouds: Cirrus clouds are wispy clouds that form at altitudes above 6,000 m or 6 km. Cirrus clouds are made of ice crystals.

2. Precipitationa. Under what conditions does Rain fall?

For rain to fall, the tiny droplets that make up clouds must collide and stick together. When droplets become large enough, they fall to Earth as rain when the air temperature is above freezing.

b. Under what conditions does Snow fall? When the air temperature is below freezing, ice crystals

can clump together and fall as snow.

c. Under what conditions does Freezing rain fall?When the air temperature is near freezing, rain can fall through layers of cold air to form sleet or freezing rain.

d. Under what conditions does Hail fall?Hail forms as layers of ice freeze onto droplets and air currents circulate these droplets inside a cloud.

F. Global Water Cycle1. Please Define the Water Cycle:

Water is constantly cycling between Earth’s surface and the atmosphere. Precipitation →Surface runoff→ Evaporation → back to Precipitation.

II. WEATHER – 28.2A. Air Pressure 1. Please Define Air Pressure:

The atmosphere exerts a force on Earth’s surface that is equal to the weight of the air above it. Air pressure is equal to this force divided by surface area.

2. When is wind created?Wind is created when air moves from an area of high pressure to an area of low pressure.

3. Global winds and pressure systemsa. What creates Large-scale global wind belts?

Large scale differences in air pressure create global wind belts.

b. What creates north-south wind circulation? Warm air rising near the equator and sinking over the poles

creates general north-south wind circulation.

c. What creates east-west deflection of wind circulation?

The Earth’s rotation on its axis produces an east-west deflection of Earth’s wind circulation.

4. Jet streamsa. Please Define Jet Stream: Narrow band of powerful, fast-moving, high-altitude air embedded in the global wind belts.

B. Pressure Systems1. What is a Low Pressure System?

A low-pressure system, also known as a low (L), is a region in the troposphere where the air pressure is lower than the surrounding air.

Low Pressure Continued…Because air flows from areas of high pressureto low areas of low pressure, air flows toward the center of a low pressure system. This inward air flow causes the air in the center of the low to rise. As the air rises, it expands and cools, and this results in cloud formation and precipitation.

2. What is a High Pressure System?A high-pressure system, also known a high (H), is a region in the troposphere where the air pressure is higher than the surrounding air. As a result, air in a high pressure system flows away from the center.

High Pressure continued…This outward flow causes the air in the center of a high to sink. Because sinking air does not lead to cloud formation, clear skies are often associated with highs.

3. Coriolis effecta. Please Define Coriolis Effect:

The effect of the rotation of the Earth on the motion of air traveling north or south from the equator. In the northern hemisphere the air is deflected to the right and the southern hemisphere air is deflected to the left.

C. Air Masses and Weather Fronts1. Please Define Air Mass:

A large volume of air that has the characteristics of the area over which is forms.

2. Where air masses originatea. Please Define Polar Air Mass: Air mass that forms in northern Canada and is cold and

dry.

b. Please Define Tropical Air Mass: Warm moist air mass that originates in the subtropics and

moves north during the Summer months.

c. Please Define Continental Air Mass: Hot and dry air mass that originates in the desert southwest or in Mexico during the Summer months and moves northward.

d. Please Define Maritime Air Mass:Moist cool air mass that originates over the Oceans and moves west to east in either Winter or Summer.

3. Where air masses meeta. Please Define Weather Fronts:

Zone along which two or more air masses interact, producing certain weather conditions.

b. Please Define Cold Front: Cold air forces warm air upward in a fast and chaotic manner, forming cumulus clouds. A cold front can also result in the formation of cumulonimbus clouds and severe storms.

c. Please Define Warm Front:A warm front rises gently above cold air, usually forming layered, stratus-type clouds or fog-a cloud with is base on the ground. Most layered stratus clouds produce steady rainfall.

d. Please Define Stationary Front:Stationary fronts form where cold and warm air masses meet and neither front advances. Stationary fronts can last for days in an area and produce clouds and prolonged precipitation.

e. Please Define Occluded Front: Occluded fronts occur when a fast-moving cold front overtakes a slow warm front. Thunderstorms and strong winds are often associated with occluded fronts.

D. Severe Weather 1. Thunderstorms

a. When do Thunderstorms form? A thunderstorm forms when warm and wet air

rises rapidly. As the rising air cools, water vapor condenses to form water droplets or ice crystals.

b. What type of Clouds form Thunderstorms? Inside the Thunderstorm cloud, the latent heat of

condensation warms the surrounding air, causing it to rise even higher. This rising air can form cumulonimbus clouds.

c. When is Lightning produced?As the air rises and sinks within the cloud, a charge separation occurs. Lightning is produced when oppositely charged particles within the cloud, between two clouds, orbetween the cloud and the ground interact.

d. What is Thunder? The surrounding air inside the thunderstorm cloud ionizes, creating an electric field that generates a lightning bolt. Hotter than the surface of the Sun, the lightning bolt causes air to expand and collapse to produce thunder.

2. Downburstsa. How are Downbursts produced? Downbursts occur when cold air descends from a cloud and hits the ground. Sometimes the downdraft spreads out when it hits the ground, forming a series of gusty winds called squalls.

3. Tornadoes and hurricanesa. How does a Tornado form?

A tornado forms in cumulonimbus clouds where strong updrafts create a vortex effect. Tornadoes form when a cold and dry air mass meets a warm and wet air mass.

b. Where do Tornadoes form?Tornadoes form on the Great Plains of the U.S., the lower Midwest, and parts of the South. In the South, tornadoes often accompany hurricanes.

c. How does a Hurricane form? Hurricanes form as tropical depressions over the warm

Atlantic waters near the coast of West Africa. They are fueled by the warm air and water in the oceans.

d. Where do Hurricanes form? Hurricanes form as tropical depressions over the warm

Atlantic waters near the coast of West Africa.

III. CLIMATE – 28.3A. Climate and Weather 1. Please Define Climate:

Climate is often defined as the long-term average weather conditions for an area- temperature, precipitation, wind patterns and other factors that affect the weather.

2. Please Define Weather: Weather is a day to day description of cloud cover or

absence of, type of precipitation, and wind direction and its speed.

3. Factors that affect climate a. Interactions within the Earth system 1.) How does a Volcano eruption affect the local climate?

Volcanoes erupt gas and ash from the lithosphere into the atmosphere. If enough gas and ash are erupted, it might also shield sunlight for days or months, affecting the climate of an area.

b. What factors determine climate? 1.) Latitude:

The primary factor that influences the climate in any given area is latitude.

2.) Direction and Strength of the Prevailing Winds: The direction and strength of the prevailing winds depend on latitude.

3.) Size of Landmass: Large landmasses such as central Asia have cold winters and hot summers. Smaller landmasses such as large Islands such as Great Britain, have mild winters and cool summers.

4.) Nearest to the Ocean:Other factors that affect climate include the distance to large bodies of water, such as an ocean.

c. Temperature1.) What determines long-term average

temperature? a.) Latitude, due to the intensity of solar radiation received is dependent on the angle with which the Sun’s rays strike the surface of the Earth.

b. Photoperiod, or the number of hours the sunlight hits the earth at any given season. More during the Summer months and less during the Winter months.

d. Ocean and land 1.) Please Define Maritime climate:

Climate strongly influenced by pressure of an ocean, tends to be mild due to moisture.

2.) Please Define Continental climate: Climate not affected by an ocean, characterized by

extremes in temperatures.

e. Precipitation 1.) What affects Precipitation?

a.) Wind and air pressure patterns affect the average precipitation of a region.

b. Precipitation is also affected by a region’s location on continent.

f. Mountains1.) Windward side of Mountains has what sort of climate?As a air mass approaches the mountains, it will rise up over them. Rising air cools, and condensation occurs. As a result, precipitation falls on the windward side of the mountains.

2.) Leeward side of a Mountain has what sort of climate?On the opposite side of the mountains, called the leeward side, the air is drier and warms as it descends. Weather on the leeward side of mountain is often warm and dry.

g. Water1.) Please Define Sea Breeze: Local wind created by temperature and pressure differences between ocean and land; wind blows toward land in the afternoon, and away from land at night.

h. Small-scale climatea. Give an example of Small-scale climates:

For example, large cities tend to be warmer than the surrounding suburbs because buildings and pavement materials heat up more rapidly than land.

B. Types of ClimatesIV. EARTH’S CHANGING CLIMATE – 28.4

A. Seasonal Changes 1. How do Seasonal Changes occur?

Seasonal changes occur as Earth revolves around the Sun. The hemisphere tilted toward the Sun experiences summer, and hemisphere tilted toward away from the Sun experiences winter.

1. How do Seasonal Changes occur?

B. Long-Term ChangesC. Causes of Climate Change

1. Periodic shifts in Earth’s orbit2. Sunspot activity3. Catastrophic events

4. The human factor 5. The carbon cycle 6. Greenhouse gases

7. Global warminga. Please Define Global Warming: Increase in average temperatures of Earth’s near-surface

air and oceans.

Arctic Ice Winter 2014

D. El Nino and La Nina1. Please Define El Nino: Periodic warming of the Pacific Ocean off the coast of western South America that changes global weather patterns.

2. Please Define La Nina: Periodic cooling of equatorial ocean surface temperature

that modify global weather patterns.

La Nina:

V. CHAPTER 28 REVIEWA. Check Concepts

1. Please do questions 37-44 on page 910.

B. Standardized Test Practice 1. Please do questions 1-8 on page

912.