WEATHER AND CLIMATE Chapter 28
EARTH’S ATMOSPHERE – 2.8 A. 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%
What are the trace gases found in our atmosphere? 1. Water vapor 2. Argon 3. Carbon dioxide 4. Ozone 5. Neon 6. Methane 7. Nitrogen oxides
2. Life and the atmosphere a. 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 and carbon dioxide reaches its maximum amount in May.
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.
Please Define Temperature Inversion: Describes the increasing temperature of air with increasing altitude.
The stratosphere a. Please Define Stratosphere: Above the troposphere and includes the ozone layer where the temperature always increases with altitude.
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.
Please Define Mesosphere: Layer of air above the Stratosphere where temperature of the air decreases.
Please Define Thermosphere: Layer above the Mesophere where the temperature of this air layer increases.
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.
Heating the Atmosphere 1. 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 reflectiveatmosphere, clouds, and the water or ice surfaces of our planet.
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.
Please Define Greenhouse Effect: Natural process in which certain gases in the atmosphere absorb and emit infrared radiation, warming the planet.
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).
Heat Absorption by Earth Surfaces 1. 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.
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.
Precipitation a. 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.
Under what conditions does Snow fall? When the air temperature is below freezing, ice crystals can clump together and fall as snow.
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.
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 Cycle 1. Please Define the Water Cycle: Water is constantly cycling between Earth’s surface and the atmosphere. Precipitation →Surface runoff→ Evaporation → back to Precipitation.
WEATHER – 28.2 A. 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.
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 systems a. 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.
Jet streams a. Please Define Jet Stream: Narrow band of powerful, fast-moving, high-altitude air embedded in the global wind belts.
Pressure Systems 1. 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 pressure to 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.
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.
Coriolis effect a. 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.
Air Masses and Weather Fronts 1. Please Define Air Mass: A large volume of air that has the characteristics of the area over which is forms.
Where air masses originate a. Please Define Polar Air Mass: Air mass that forms in northern Canada and is cold and dry.
Please Define Tropical Air Mass: Warm moist air mass that originates in the subtropics and moves north during the Summer months.
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.
Please Define Maritime Air Mass: Moist cool air mass that originates over the Oceans and moves west to east in either Winter or Summer.
Where air masses meet a. 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.
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.
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.
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.
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, or between the cloud and the ground interact.
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.