eTextbook: Essentials of Meteorology - Chapter 1: Earth’s Atmosphere
The Atmosphere and the Scientific Method
The Earth’s atmosphere is a delicate life-giving blanket of air surrounding the planet; it influences everything we see and hear and is essential for survival.
The Sun provides warmth and energy that drives weather and climate.
The scientific method in atmospheric science: pose a question, form a hypothesis, make predictions, test predictions with observations and experiments, and use quantitative tests to verify results.
Weather forecasting relies on observations, laboratory physics, and numerical models run on computers; models are validated by their ability to reproduce past weather and predict future conditions.
Weather, Climate, and Meteorology
Weather: the state of the atmosphere at a particular time and place; composed of weather elements:
air temperature
air pressure
humidity (water vapor)
clouds
precipitation
visibility
wind
Climate: the accumulation of daily and seasonal weather events (and their extremes) over a long period; includes averages and extremes.
Meteorology: the study of the atmosphere and its phenomena; origin traced to Aristotle’s Meteorologica.
Key climate/weather facts: weather can change in minutes; climate evolves over long times; both are linked to the atmosphere’s physics and chemistry.
Composition of Earth’s Atmosphere
Major dry-air constituents (near the surface):
ext{N}2 \approx 78.08 ext{%}, \text{O}2 \approx 20.95 ext{%}
Small amounts: Argon (Ar) ~ 0.93%, Neon (Ne) ~ 0.0018%, Helium (He) ~ 0.0005%, Xenon (Xe) ~ 0.000009%
Water vapor varies spatially and temporally: 0 ext{% to }4 ext{%} by volume.
Carbon dioxide: about 0.04 ext{%} (roughly 400 ppm); CO₂ is rising due to fossil-fuel burning and other processes.
Other important gases: methane (CH₄), nitrous oxide (N₂O), ozone (O₃); ozone distribution differs by altitude (protects from UV in the stratosphere but is a pollutant at the surface in photochemical smog).
Water vapor and CO₂ are key greenhouse gases; water vapor also stores/releases latent heat during phase changes.
Aerosols and pollutants: solid/liquid particles (dust, smoke, soot) and gases (NO₂, CO, SO₂) that affect visibility, air quality, and chemistry.
The atmosphere contains a protective ozone layer in the stratosphere; photochemical processes can deplete ozone, especially due to CFCs.
Vertical Structure of the Atmosphere
The atmosphere is thin but extends hundreds of kilometers; ~99% of the mass is within the lower ~30 km.
Pressure and density decrease with height:
At sea level: p_0 \approx 1013.25\ \text{mb} = 1013.25\ \text{hPa} = 29.92\ \text{inHg}
Atmospheric pressure falls rapidly with height; by about 5.5 km, pressure is roughly \approx 500\ \text{mb}; by 50 km, ~1 mb.
Air density decreases with height because there are fewer air molecules above.
Temperature profile (average):
Troposphere: temperature generally decreases with height (lapse rate ≈ 6.5^\circ\text{C} \text{ per } 1000\ \text{m}).
Isothermal layer: near the upper part of the troposphere, lapse rate approaches zero.
Tropopause: boundary between troposphere and stratosphere; height varies with latitude and season.
Stratosphere: temperature increases with height due to ozone absorbing UV energy (temperature inversion).
Mesosphere: temperature decreases with height; mesopause is the coldest part of the atmosphere.
Thermosphere: very high temperatures but extremely low density; solar energy absorption heats the few molecules present.
Exosphere: outermost region, where atmosphere gradually fades into space.
Key layers and terms:
Homosphere: lower, well-mixed region where major gases are fairly uniform.
Heterosphere: upper region with light gases dominating at high altitudes; diffusion becomes important.
Ionosphere: electrified region with many ions/free electrons; important for radio wave propagation.
Tropopause and jet streams mark boundaries and regions of rapid atmospheric changes.
The Energy Connection: Weather, Latent Heat, and Greenhouse Effect
Latent heat: energy absorbed or released during phase changes of water (evaporation, condensation, freezing, melting); a major energy source for storms.
The greenhouse effect: water vapor and CO₂ trap outgoing infrared energy, warming the surface; essential for maintaining habitable temperatures.
The Atmosphere in Motion: Weather Maps and Fronts
Weather maps show pressure systems and fronts:
Isobars: lines of equal pressure; winds tend to flow around pressure systems.
High-pressure centers (H): clockwise and outward winds in the Northern Hemisphere; generally clear skies.
Low-pressure centers (L): counterclockwise and inward winds in the Northern Hemisphere; clouds and precipitation common.
Fronts (boundaries between air masses):
Cold front: blue line with triangles; advances into warm air, often producing thunderstorms.
Warm front: red line with half-circles; gentle precipitation as warm air rises over cooler air.
Occluded front: purple line with alternating triangles and circles; occurs when a cold front catches a warm front.
Weather systems in the mid-latitudes are steered by upper-level winds; fronts bring organized weather (rain, storms, etc.).
Weather and Climate in Our Lives
Weather and climate influence clothing, agriculture, energy use, and daily activities.
Extreme events (droughts, floods, heat/cold waves, hurricanes, tornadoes) have large economic and social impacts.
Long-term climate trends (e.g., warming) are studied with climate models and observations.
The Atmosphere: History, Technology, and Measurement
Historical development:
Instruments: hygrometer, thermometer, barometer; later upper-air observations (balloons) and jet streams discovered.
Telegraph (1843) enabled weather observations to be transmitted; early weather maps with isobars (1869).
Numerical weather prediction began in the 1950s with computer models.
Doppler radar (mid-1990s) improved precipitation, wind, and storm analysis.
Weather satellites (first TIROS launched in 1960) expanded data for clouds, storms, and water vapor.
Radiosonde observations:
A radiosonde measures temperature, humidity, and pressure as it ascends with a balloon;
Rawinsonde adds wind measurements via GPS-tracked balloon data; sounding is the collected profile.
Modern observations combine radiosondes, satellites, radar, and surface stations to forecast weather.
Focus: Carbon Dioxide, Ozone, Aerosols, and Climate Forcing
Carbon Dioxide (CO₂):
Preindustrial CO₂ ~ 280 ppm; today around 400–410 ppm and rising (~0.5% per year).
CO₂ sources: burning fossil fuels, deforestation; sinks include oceans and vegetation.
CO₂ concentration has risen roughly 30% since 1958 (Mauna Loa; long-term record).
The CO₂ cycle involves exchanges with oceans, land, and biosphere; atmospheric CO₂ drives long-term climate change in models.
Ozone (O₃):
Stratospheric ozone protects against UV radiation; ~97% of atmospheric ozone is in the stratosphere.
CFCs and related compounds can deplete stratospheric ozone, forming ozone holes (Antarctica) in spring.
Aerosols and surface pollutants:
Aerosols are airborne particles (dust, smoke, sulfate, etc.) affecting visibility and chemistry.
Surface pollutants include NO₂, CO, hydrocarbons; can contribute to photochemical smog and ozone formation.
Additional Reference Concepts
The exosphere is the outer limit of the atmosphere; hydrogen and helium can escape into space.
The temperature profile distinguishes layers: troposphere (weather), stratosphere (ozone heating), mesosphere, thermosphere (ionization/auroras), exosphere.
For quick recall: the four most abundant gases today are ext{N}2, ext{O}2, ext{Argon (Ar)}, ext{CO}_2 with water vapor varying significantly by location and time.
Ozone hole (seasonal): occurs over the Antarctic stratosphere; measured in Dobson Units; 1 DU ≈ thickness of ozone layer if spread at Earth’s surface (≈ 0.01 cm).
An instrument example: radiosonde tracks vertical profiles; GPS improves wind calculations for rawinsondes.
Quick Summary (Key Takeaways)
Weather is the short-term state of the atmosphere; climate is the long-term average and extremes.
The atmosphere is composed mainly of N₂ and O₂, with water vapor and CO₂ as critical greenhouse components; their levels shape Earth's energy balance.
The atmosphere is structured into layers (troposphere, stratosphere, mesosphere, thermosphere, exosphere) with pressure and temperature profiles that vary with height.
Weather maps use isobars, highs, lows, and fronts to describe and forecast weather; mid-latitude systems are driven by horizontal pressure differences and the Earth’s rotation.
Human activities are changing atmospheric composition (notably CO₂) and influencing climate, with important roles for other greenhouse gases, ozone chemistry, aerosols, and land-use changes.
Key Terms to Know
atmosphere, weather, weather elements, climate, meteorology
middle latitudes, middle-latitude cyclonic storm, hurricane, thunderstorms, tornadoes
wind, wind direction, wind speed, front
outgassing, nitrogen, oxygen
lapse rate, temperature inversion, radiosonde, troposphere, stratosphere, tropopause, mesosphere, thermosphere, ionosphere
ozone (O₃), aerosols, pollutants, NO₂, CO, SO₂
CO₂ cycle, greenhouse gases, Mauna Loa, Dobson Units, ozone hole
exosphere, homosphere, heterosphere
jet streams, isobars, fronts, storms
The Earth’s atmosphere is a delicate life-giving blanket of air surrounding the planet; it influences everything we see and hear and is essential for survival.
The Sun provides warmth and energy that drives weather and climate.
The scientific method in atmospheric science: pose a question, form a hypothesis, make predictions, test predictions with observations and experiments, and use quantitative tests to verify results.
Weather forecasting relies on observations, laboratory physics, and numerical models run on computers; models are validated by their ability to reproduce past weather and predict future conditions.
Weather, Climate, and Meteorology
Weather: the state of the atmosphere at a particular time and place; composed of weather elements:
air temperature
air pressure
humidity (water vapor)
clouds
precipitation
visibility
wind
Climate: the accumulation of daily and seasonal weather events (and their extremes) over a long period; includes averages and extremes.
Meteorology: the study of the atmosphere and its phenomena; origin traced to Aristotle’s Meteorologica.
Key climate/weather facts: weather can change in minutes; climate evolves over long times; both are linked to the atmosphere’s physics and chemistry.
Composition of Earth’s Atmosphere
Major dry-air constituents (near the surface):
\text{N}2 \approx 78.08\%, \text{O}2 \approx 20.95\%
Small amounts: Argon (Ar) ~ 0.93%, Neon (Ne) ~ 0.0018%, Helium (He) ~ 0.0005%, Xenon (Xe) ~ 0.000009%
Water vapor varies spatially and temporally: 0\% \text{ to } 4\%\ by volume.
Carbon dioxide: about 0.04\%\ (roughly 400 ppm); CO₂ is rising due to fossil-fuel burning and other processes.
Other important gases: methane (CH4), nitrous oxide (N2O), ozone (O_3); ozone distribution differs by altitude (protects from UV in the stratosphere but is a pollutant at the surface in photochemical smog).
Water vapor and CO₂ are key greenhouse gases; water vapor also stores/releases latent heat during phase changes.
Aerosols and pollutants: solid/liquid particles (dust, smoke, soot) and gases (NO2, CO, SO2) that affect visibility, air quality, and chemistry.
The atmosphere contains a protective ozone layer in the stratosphere; photochemical processes can deplete ozone, especially due to CFCs.
Vertical Structure of the Atmosphere
The atmosphere is thin but extends hundreds of kilometers; ~99% of the mass is within the lower ~30 km.
Pressure and density decrease with height:
At sea level: p_0 \approx 1013.25\ \text{mb} = 1013.25\ \text{hPa} = 29.92\ \text{inHg}
Atmospheric pressure falls rapidly with height; by about 5.5 km, pressure is roughly \approx 500\ \text{mb}; by 50 km, ~1 mb.
Air density decreases with height because there are fewer air molecules above.
Temperature profile (average):
Troposphere: temperature generally decreases with height (lapse rate (\approx 6.5^\circ\text{C} \text{ per } 1000\ \text{m})).
Isothermal layer: near the upper part of the troposphere, lapse rate approaches zero.
Tropopause: boundary between troposphere and stratosphere; height varies with latitude and season.
Stratosphere: temperature increases with height due to ozone absorbing UV energy (temperature inversion).
Mesosphere: temperature decreases with height; mesopause is the coldest part of the atmosphere.
Thermosphere: very high temperatures but extremely low density; solar energy absorption heats the few molecules present.
Exosphere: outermost region, where atmosphere gradually fades into space.
Key layers and terms:
Homosphere: lower, well-mixed region where major gases are fairly uniform.
Heterosphere: upper region with light gases dominating at high altitudes; diffusion becomes important.
Ionosphere: electrified region with many ions/free electrons; important for radio wave propagation.
Tropopause and jet streams mark boundaries and regions of rapid atmospheric changes.
The Energy Connection: Weather, Latent Heat, and Greenhouse Effect
Latent heat: energy absorbed or released during phase changes of water (evaporation, condensation, freezing, melting); a major energy source for storms.
The greenhouse effect: water vapor and CO₂ trap outgoing infrared energy, warming the surface; essential for maintaining habitable temperatures.
The Atmosphere in Motion: Weather Maps and Fronts
Weather maps show pressure systems and fronts:
Isobars: lines of equal pressure; winds tend to flow around pressure systems.
High-pressure centers (H): clockwise and outward winds in the Northern Hemisphere; generally clear skies.
Low-pressure centers (L): counterclockwise and inward winds in the Northern Hemisphere; clouds and precipitation common.
Fronts (boundaries between air masses):
Cold front: blue line with triangles; advances into warm air, often producing thunderstorms.
Warm front: red line with half-circles; gentle precipitation as warm air rises over cooler air.
Occluded front: purple line with alternating triangles and circles; occurs when a cold front catches a warm front.
Weather systems in the mid-latitudes are steered by upper-level winds; fronts bring organized weather (rain, storms, etc.).
Weather and Climate in Our Lives
Weather and climate influence clothing, agriculture, energy use, and daily activities.
Extreme events (droughts, floods, heat/cold waves, hurricanes, tornadoes) have large economic and social impacts.
Long-term climate trends (e.g., warming) are studied with climate models and observations.
The Atmosphere: History, Technology, and Measurement
Historical development:
Instruments: hygrometer, thermometer, barometer; later upper-air observations (balloons) and jet streams discovered.
Telegraph (1843) enabled weather observations to be transmitted; early weather maps with isobars (1869).
Numerical weather prediction began in the 1950s with computer models.
Doppler radar (mid-1990s) improved precipitation, wind, and storm analysis.
Weather satellites (first TIROS launched in 1960) expanded data for clouds, storms, and water vapor.
Radiosonde observations:
A radiosonde measures temperature, humidity, and pressure as it ascends with a balloon;
Rawinsonde adds wind measurements via GPS-tracked balloon data; sounding is the collected profile.
Modern observations combine radiosondes, satellites, radar, and surface stations to forecast weather.
Focus: Carbon Dioxide, Ozone, Aerosols, and Climate Forcing
Carbon Dioxide (CO₂):
Preindustrial CO₂ ~ 280 ppm; today around 400–410 ppm and rising (~0.5% per year).
CO₂ sources: burning fossil fuels, deforestation; sinks include oceans and vegetation.
CO₂ concentration has risen roughly 30% since 1958 (Mauna Loa; long-term record).
The CO₂ cycle involves exchanges with oceans, land, and biosphere; atmospheric CO₂ drives long-term climate change in models.
Ozone (O₃):
Stratospheric ozone protects against UV radiation; ~97% of atmospheric ozone is in the stratosphere.
CFCs and related compounds can deplete stratospheric ozone, forming ozone holes (Antarctica) in spring.
Aerosols and surface pollutants:
Aerosols are airborne particles (dust, smoke, sulfate, etc.) affecting visibility and chemistry.
Surface pollutants include NO_2, CO, hydrocarbons; can contribute to photochemical smog and ozone formation.
Additional Reference Concepts
The exosphere is the outer limit of the atmosphere; hydrogen and helium can escape into space.
The temperature profile distinguishes layers: troposphere (weather), stratosphere (ozone heating), mesosphere, thermosphere (ionization/auroras), exosphere.
For quick recall: the four most abundant gases today are \text{N}2, \text{O}2, \text{Argon (Ar)}, \text{CO}_2\ with water vapor varying significantly by location and time.
Ozone hole (seasonal): occurs over the Antarctic stratosphere; measured in Dobson Units; 1 DU ≈ thickness of ozone layer if spread at Earth’s surface (≈ 0.01 cm).
An instrument example: radiosonde tracks vertical profiles; GPS improves wind calculations for rawinsondes.
Quick Summary (Key Takeaways)
Weather is the short-term state of the atmosphere; climate is the long-term average and extremes.
The atmosphere is composed mainly of N₂ and O₂, with water vapor and CO₂ as critical greenhouse components; their levels shape Earth's energy balance.
The atmosphere is structured into layers (troposphere, stratosphere, mesosphere, thermosphere, exosphere) with pressure and temperature profiles that vary with height.
Weather maps use isobars, highs, lows, and fronts to describe and forecast weather; mid-latitude systems are driven by horizontal pressure differences and the Earth’s rotation.
Human activities are changing atmospheric composition (notably CO₂) and influencing climate, with important roles for other greenhouse gases, ozone chemistry, aerosols, and land-use changes.
Key Terms and Definitions
atmosphere: The protective blanket of air surrounding Earth, vital for life.
weather: The current state of the atmosphere at a specific time and place.
weather elements: The specific conditions defining weather: temperature, pressure, humidity, clouds, precipitation, visibility, and wind.
climate: The long-term average and extremes of weather events over many years.
meteorology: The study of Earth's atmosphere and its phenomena.
middle latitudes: Regions between 30^\circ\ and 60^\circ\ latitude, known for complex weather systems and fronts.
middle-latitude cyclonic storm: A large low-pressure storm in mid-latitudes, marked by rotating winds, fronts, and precipitation.
hurricane: A powerful tropical storm with winds over 74 mph (119 km/h), forming over warm oceans.
thunderstorms: Storms with lightning, thunder, strong winds, and often heavy rain; usually linked to cold fronts.
tornadoes: Violent, spinning columns of air extending from a thunderstorm to the ground.
wind: Air movement caused by pressure differences.
wind direction: The direction from which the wind blows.
wind speed: How fast the air is moving.
front: A boundary between different air masses, often causing weather changes.
outgassing: Release of gases from Earth's interior, like from volcanoes.
nitrogen (N_2): An unreactive gas making up ~78% of Earth's dry atmosphere.
oxygen (O_2): A reactive gas essential for life, making up ~21% of the dry atmosphere.
lapse rate: The rate at which air temperature decreases with altitude (e.g., in the troposphere).
temperature inversion: When temperature increases with height, instead of decreasing, often trapping pollutants.
radiosonde: A balloon-borne instrument measuring atmospheric temperature, humidity, and pressure.
troposphere: The lowest atmospheric layer where most weather occurs; temperature decreases with height.
stratosphere: The layer above the troposphere where temperature increases with height due to the ozone layer absorbing UV.
tropopause: The boundary between the troposphere and stratosphere.
mesosphere: The layer above the stratosphere where temperature decreases with height; the coldest part of the atmosphere.
thermosphere: The outermost layer (before exosphere) with very high temperatures but extremely thin air.
ionosphere: An electrified region in the upper atmosphere important for radio waves due to ionized gases.
ozone (O_3): A gas that protects from UV in the stratosphere but is a pollutant at ground level.
aerosols: Tiny airborne solid or liquid particles that affect visibility and air quality.
pollutants: Harmful substances in the atmosphere, like gases (NO2, CO, SO2) and particles.
Nitrogen dioxide (NO_2): A gas pollutant contributing to smog and acid rain.
Carbon monoxide (CO): A toxic gas from incomplete burning of carbon materials.
Sulfur dioxide (SO_2): A pungent gas, a main cause of acid rain and respiratory issues.
CO₂ cycle: The natural exchange of carbon dioxide between Earth's systems.
greenhouse gases: Gases (like CO₂, water vapor) that trap heat in the atmosphere, warming Earth.
Mauna Loa: An observatory providing a key record of rising atmospheric CO₂.
Dobson Units: A unit to measure the total amount of ozone in the atmosphere.
ozone hole: A severe thinning of the ozone layer, especially over Antarctica in spring.
exosphere: The very outermost atmospheric layer where gases escape into space.
homosphere: The lower atmosphere where gases are well-mixed.
heterosphere: The upper atmosphere where gases separate by weight.
jet streams: Fast, narrow air currents in the upper troposphere that steer weather.
isobars: Lines on a weather map connecting points of equal atmospheric pressure.
storms: Any disturbed atmospheric state with strong winds, often precipitation, thunder, or lightning.
Comprehensive Study Guide: Earth's Atmosphere
This guide summarizes the core concepts of atmospheric science, focusing on essential information for a test.
I. Fundamentals of the Atmosphere and Scientific Inquiry
Earth's Atmosphere: A vital envelope of air, essential for life, driven by solar energy.
Scientific Method: Understand its application in atmospheric science (question, hypothesis, prediction, test, quantitative verification).
Weather Forecasting: Relies on observations, physics, and numerical models validated by past and future predictions.
II. Defining Weather, Climate, and Meteorology
Weather: The current state of the atmosphere at a specific time and place.
Weather Elements: Air temperature, air pressure, humidity, clouds, precipitation, visibility, wind.
Climate: Long-term average and extremes of weather events over a significant period.
Meteorology: The study of the atmosphere and its phenomena.
Key Distinction: Weather changes rapidly; climate evolves slowly.
III. Composition of the Atmosphere
Major Dry-Air Constituents (near surface):
Nitrogen (\text{N}_2): ~$78.08\%
Oxygen (\text{O}_2): ~$20.95\%
Argon (\text{Ar}): ~$0.93\%
Variable Gases:
Water Vapor: Varies \text{0}% to \text{4}%\ by volume; crucial for latent heat and greenhouse effect.
Carbon Dioxide (\text{CO}_2): Approximately \text{0.04}%\ (~400 ppm) and rising; a key greenhouse gas.
Other Greenhouse Gases: Methane (\text{CH}4), Nitrous Oxide (\text{N}2\text{O}), Ozone (\text{O}_3).
Ozone (\text{O}_3):
Stratospheric Ozone: Protects from UV radiation.
Surface Ozone: Pollutant (photochemical smog).
Aerosols and Pollutants: Solid/liquid particles (dust, smoke) and gases (\text{NO}2, CO, \text{SO}2) affecting visibility and air quality.
IV. Vertical Structure of the Atmosphere
Overall Structure: Thin, ~99% of mass in lower ~30 km.
Pressure and Density: Both decrease rapidly with height.
Sea level pressure: \approx 1013.25\ \text{mb}.
Temperature Profile (Layers):
Troposphere: Temperature decreases with height (lapse rate \approx 6.5^\circ\text{C} \text{ per } 1000\ \text{m}); where most weather occurs.
Tropopause: Boundary between troposphere and stratosphere.
Stratosphere: Temperature increases with height (inversion) due to ozone absorbing UV.
Mesosphere: Temperature decreases with height; coldest layer.
Thermosphere: Very high temperatures, but extremely low density.
Exosphere: Outermost layer where gases escape into space.
Other Key Layers/Regions:
Homosphere: Lower, well-mixed region.
Heterosphere: Upper region where gases separate by weight.
Ionosphere: Electrified region, important for radio waves.
V. Energy Connections
Latent Heat: Energy absorbed/released during water phase changes (e.g., evaporation, condensation, freezing, melting); powers storms.
Greenhouse Effect: Water vapor and \text{CO}_2 trap outgoing infrared energy, warming Earth's surface and maintaining habitable temperatures.
VI. Atmospheric Motion: Weather Maps and Fronts
Weather Maps: Display pressure systems and fronts.
Isobars: Lines of equal pressure.
High-Pressure Centers (H): Clear skies; clockwise, outward winds (Northern Hemisphere).
Low-Pressure Centers (L): Clouds, precipitation; counterclockwise, inward winds (Northern Hemisphere).
Fronts (Boundaries between Air Masses):
Cold Front: Blue line with triangles; often brings thunderstorms.
Warm Front: Red line with half-circles; gentle precipitation.
Occluded Front: Purple with alternating triangles/circles; cold front overtakes warm front.
Mid-Latitude Systems: Steered by upper-level winds (jet streams).
VII. Climate Change and Human Impact
Rising \text{CO}_2: From preindustrial ~$280\ \text{ppm}\ to ~$400-410\ \text{ppm}\ today (Mauna Loa record). Driven by fossil fuels, deforestation.
Ozone Depletion: Stratospheric ozone layer depleted by CFCs, leading to seasonal ozone holes (e.g., Antarctica).
Climate Forcing: Human activities significantly alter atmospheric composition, influencing long-term climate trends.
VIII. Key Terms to Know (from the full list)
atmosphere, weather, climate, meteorology
weather elements (all 7)
troposphere, stratosphere, mesosphere, thermosphere, exosphere
tropopause, lapse rate, temperature inversion
nitrogen (\text{N}2), oxygen (\text{O}2), water vapor, carbon dioxide (\text{CO}2), ozone (\text{O}3)
greenhouse gases, greenhouse effect, latent heat
isobars, high-pressure, low-pressure, cold front, warm front, occluded front
radiosonde, rawinsonde, Doppler radar, weather satellites
ozone hole, Dobson Units, aerosols
I. Fundamentals of the Atmosphere and Scientific Inquiry
Atmosphere: Earth's protective air blanket, essential for life, driven by solar energy.
Scientific Method in Atmospheric Science: Involves posing questions, forming hypotheses, making predictions, testing with observations/experiments, and verifying quantitatively.
Weather Forecasting: Uses observations, physics, and numerical computer models, validated by their ability to reproduce past and predict future weather.
II. Defining Weather, Climate, and Meteorology
Weather: Current atmospheric state at a specific time and place.
Weather Elements: Air temperature, pressure, humidity, clouds, precipitation, visibility, and wind.
Climate: Long-term accumulation of daily/seasonal weather events (averages and extremes).
Meteorology: The study of the atmosphere and its phenomena.
Key Distinction: Weather changes quickly; climate evolves over long periods.
III. Composition of the Atmosphere
Major Dry-Air Constituents (near surface):
Nitrogen (\text{N}_2): ~78.08\%
Oxygen (\text{O}_2): ~20.95\%
Argon (\text{Ar}): ~0.93\%
Variable Gases:
Water Vapor: Varies \text{0}% to \text{4}%\ by volume; crucial for latent heat and the greenhouse effect.
Carbon Dioxide (\text{CO}_2): ~0.04\% (~400 ppm) and rising; a key greenhouse gas from fossil fuels/deforestation.
Other Greenhouse Gases: Methane (\text{CH}4), Nitrous Oxide (\text{N}2\text{O}), Ozone (\text{O}_3).
Ozone (\text{O}_3):
Stratospheric Ozone: Protects from UV radiation.
Surface Ozone: A pollutant (photochemical smog).
Aerosols and Pollutants: Particles (dust, smoke) and gases (\text{NO}2, CO, \text{SO}2) affecting visibility and air quality.
IV. Vertical Structure of the Atmosphere
Overall Structure: Thin, ~99% of mass within lower ~30 km.
Pressure and Density: Both decrease rapidly with height.
Sea level pressure: \approx 1013.25\ \text{mb}.
Temperature Profile (Layers):
Troposphere: Temperature decreases with height (lapse rate \approx 6.5^\circ\text{C} \text{ per } 1000\ \text{m}); most weather occurs here.
Tropopause: Boundary between troposphere and stratosphere.
Stratosphere: Temperature increases with height (inversion) due to ozone absorbing UV.
Mesosphere: Temperature decreases with height; coldest layer.
Thermosphere: Very high temperatures, but extremely low density.
Exosphere: Outermost layer where gases escape into space.
Other Key Layers/Regions:
Homosphere: Lower, well-mixed region.
Heterosphere: Upper region where gases separate by weight.
Ionosphere: Electrified region, important for radio waves.
V. Energy Connections
Latent Heat: Energy absorbed/released during water phase changes (e.g., evaporation, condensation); a major energy source for storms.
Greenhouse Effect: Water vapor and \text{CO}_2 trap outgoing infrared energy, warming Earth's surface for habitable temperatures.
VI. Atmospheric Motion: Weather Maps and Fronts
Weather Maps: Display pressure systems and fronts.
Isobars: Lines of equal pressure.
High-Pressure Centers (H): Clear skies; clockwise, outward winds (Northern Hemisphere).
Low-Pressure Centers (L): Clouds, precipitation; counterclockwise, inward winds (Northern Hemisphere).
Fronts (Boundaries between Air Masses):
Cold Front: Blue line with triangles; often brings thunderstorms as cold air advances.
Warm Front: Red line with half-circles; gentle precipitation as warm air rises.
Occluded Front: Purple with alternating triangles/circles; cold front overtakes warm front.
Mid-Latitude Systems: Steered by upper-level winds (jet streams).
VII. Climate Change and Human Impact
Rising \text{CO}_2: Increased from preindustrial ~$280\ \text{ppm}\, to ~$400-410\ \text{ppm}\, today (Mauna Loa record), primarily from fossil fuels and deforestation.
Ozone Depletion: Stratospheric ozone depleted by CFCs, forming seasonal ozone holes (e.g., Antarctica).
Climate Forcing: Human activities significantly altering atmospheric composition, affecting long-term climate trends.
VIII. Key Terms to Know for the Test
atmosphere, weather, climate, meteorology
weather elements (all 7: temperature, pressure, humidity, clouds, precipitation, visibility, wind)
troposphere, stratosphere, mesosphere, thermosphere, exosphere
tropopause, lapse rate, temperature inversion
nitrogen (\text{N}2), oxygen (\text{O}2), water vapor, carbon dioxide (\text{CO}2), ozone (\text{O}3)
greenhouse gases, greenhouse effect, latent heat
1. Atmosphere Basics and Scientific Method
The Earth's atmosphere is a protective layer of air vital for life. It gets warmth and energy, which drives weather and climate, from the Sun.
Scientific Method for Weather:
Ask a Question: Identify something to investigate.
Form a Hypothesis: Make an educated guess or explanation.
Predict: Foresee what will happen if the hypothesis is true.
Test: Use observations and experiments to check your prediction.
Verify: Use numbers to confirm your results.
Weather Forecasting: Uses real-time observations, physics rules, and computer models. These models are proven accurate by showing they can predict past weather and forecast future conditions.
2. Weather, Climate, and Meteorology
Weather: What the atmosphere is like right now, in a specific spot. It's made of these elements:
Air temperature
Air pressure
Humidity (how much water vapor is in the air)
Clouds
Precipitation (rain, snow, etc.)
Visibility (how far you can see)
Wind (its direction and speed)
Climate: The usual weather patterns and extreme events built up over a long time (like 30 years). It includes averages and records.
Meteorology: The study of the atmosphere and weather events, first studied by Aristotle.
Key Difference: Weather changes quickly (minutes); climate changes slowly (long periods). Both depend on the atmosphere's physical and chemical rules.
3. What the Atmosphere is Made Of
Major Dry-Air Gases (near ground):
Nitrogen ( ext{N}_2): ~78.08 ext{%}
Oxygen ( ext{O}_2): ~20.95 ext{%}
Argon ( ext{Ar}): ~0.93 ext{%}
(Other tiny amounts: Neon, Helium, Xenon.)
Variable Gases (amounts change):
Water Vapor: Varies from 0 ext{%}
to 4 ext{%}
. It's a key greenhouse gas and releases/stores energy during water's phase changes.Carbon Dioxide ( ext{CO}_2): About 0.04 ext{%} (~400 ppm) and rising. It traps heat and comes from burning fossil fuels.
Other Greenhouse Gases: Methane ( ext{CH}4), Nitrous Oxide ( ext{N}2 ext{O}), Ozone ( ext{O}_3). They also trap heat.
Ozone ( ext{O}_3):
In Stratosphere (high up): Protects Earth from harmful UV radiation.
At Surface (low down): Is a pollutant in smog.
Aerosols & Pollutants: Tiny solid/liquid particles (dust, smoke) and harmful gases ( ext{NO}2, CO, ext{SO}2) that affect air quality and how far you can see.
4. Atmosphere's Vertical Layers
General Structure: The atmosphere is thin; most of its mass (~99 ext{%}) is in the lowest ~30 ext{ km}.
Pressure & Density: Both get lower as you go higher because there are fewer air molecules.
Sea Level Pressure: About 1013.25 ext{ mb}.
Pressure drops by half every ~5.5 ext{ km}. By 50 ext{ km}, it's only ~1 ext{ mb}.
Temperature Layers (from ground up):
Troposphere: Temperature usually drops with height (about 6.5^ ext{o} ext{C}
per 1000 ext{ m}). Most weather happens here.Tropopause: The boundary between the troposphere and stratosphere.
Stratosphere: Temperature rises with height (temperature inversion) because ozone absorbs UV light.
Mesosphere: Temperature drops with height. It's the coldest layer.
Thermosphere: Very hot, but the air is super thin. Solar energy heats the few molecules present.
Exosphere: The very top layer, where air fades into space. Light gases (hydrogen, helium) can escape.
Other Important Regions:
Homosphere: Lower part where gases are well-mixed.
Heterosphere: Upper part where gases separate by weight.
Ionosphere: An electrified region within the mesosphere/thermosphere, important for radio signals.
The tropopause and jet streams mark areas of fast changes in the atmosphere.
5. Energy and Climate Connection
Latent Heat: Energy absorbed or released when water changes state (like freezing, melting, evaporating, condensing). It's a huge energy source for storms.
Greenhouse Effect: Water vapor and ext{CO}_2
trap heat (infrared energy) leaving Earth, warming the surface. This is vital for keeping Earth warm enough to live on.
6. Weather Maps and Fronts
Weather Maps: Show pressure systems and fronts to help predict weather.
Isobars: Lines connecting points of equal air pressure. Winds generally follow these lines.
High-Pressure Centers (H): Usually mean clear skies. Winds blow clockwise and outwards in the Northern Hemisphere.
Low-Pressure Centers (L): Often bring clouds and rain. Winds blow counterclockwise and inwards in the Northern Hemisphere.
Fronts (where different air masses meet):
Cold Front: (Blue line with triangles) Cold air pushes into warm air. Often brings thunderstorms.
Warm Front: (Red line with half-circles) Warm air rides over cooler air. Causes long, gentle rain.
Occluded Front: (Purple line with alternating triangles and circles) A cold front catches a warm front, lifting the warm air.
Weather systems in the mid-latitudes are moved by strong winds high up in the atmosphere (jet streams); fronts create organized weather (rain, storms).
7. Climate Change and Human Impact
Carbon Dioxide ( ext{CO}_2) Rise: Pre-industrial levels were ~280 ext{ ppm}; today, it's ~400-410 ext{ ppm} and growing ~0.5 ext{%}
yearly (Mauna Loa record). Caused by burning fossil fuels and removing forests. It drives long-term climate change.Ozone Depletion: CFCs (chemicals) reduce the protective ozone layer in the stratosphere, creating "ozone holes" (like over Antarctica in spring).
Climate Forcing: Human activities change the atmosphere's makeup (greenhouse gases, aerosols), which greatly affects long-term climate trends.
8. Key Terms to Know
atmosphere: Earth's protective air layer.
weather: Current state of the atmosphere.
weather elements: Temperature, pressure, humidity, clouds, precipitation, visibility, wind.
climate: Long-term average weather.
meteorology: Study of atmosphere and weather.
middle latitudes: Regions between 30^ ext{o}
and 60^ ext{o}
latitude.middle-latitude cyclonic storm: Large low-pressure storm with fronts.
hurricane: Strong tropical storm over oceans (>74 ext{ mph} winds).
thunderstorms: Storms with lightning, thunder, heavy rain.
tornadoes: Violent, spinning air columns from storms to ground.
wind: Air movement due to pressure differences.
wind direction: Where wind comes from.
wind speed: How fast wind moves.
front: Boundary between air masses.
outgassing: Gases released from Earth's interior.
nitrogen ( ext{N}_2): ~78 ext{%}
of dry air, unreactive.oxygen ( ext{O}_2): ~21 ext{%}
of dry air, essential for life.lapse rate: How temperature changes with height (usually drops).
temperature inversion: Temperature rises with height (traps pollutants).
radiosonde: Balloon tool measuring temperature, humidity, pressure.
troposphere: Lowest layer; most weather, temperature drops with height.
stratosphere: Layer above troposphere; ozone heats it, temperature rises with height.
tropopause: Boundary between troposphere and stratosphere.
mesosphere: Above stratosphere; temperature drops, coldest layer.
thermosphere: Outermost layer; very hot but thin air.
ionosphere: Electrified region, important for radio waves.
ozone ( ext{O}_3): Protects from UV (stratosphere), pollutant (surface).
aerosols: Tiny airborne particles (dust, smoke).
pollutants: Harmful substances in air (e.g., ext{NO}2, CO, ext{SO}2).
Nitrogen dioxide ( ext{NO}_2): Gas causing smog/acid rain.
Carbon monoxide (CO): Toxic gas from burning fuels.
Sulfur dioxide ( ext{SO}_2): Gas causing acid rain/breathing issues.
CO$_2$ cycle: Natural exchange of carbon dioxide.
greenhouse gases: Gases that trap heat (e.g., ext{CO}_2, water vapor).
Mauna Loa: Observatory tracking ext{CO}_2
increase.Dobson Units: Unit for measuring ozone amount.
ozone hole: Seasonal thinning of ozone layer (Antarctica).
exosphere: Outermost layer where gases escape.
homosphere: Lower, well-mixed atmosphere.
heterosphere: Upper atmosphere where gases separate.
jet streams: Fast high-altitude winds steering weather.
isobars: Lines of equal pressure on maps.
storms: Disturbed atmospheric state with strong winds/precipitation.
summarized notes
1. Introduction to Earth's Atmosphere & Scientific Study
Earth's Atmosphere: A protective layer of air vital for life, energized by the Sun, which drives all weather and climate.
Scientific Method for Weather & Climate:
Ask a Question: Identify what needs investigation.
Form a Hypothesis: Create a testable explanation.
Predict: Foresee the outcomes if the hypothesis is correct.
Test: Conduct observations and experiments.
Verify: Use quantitative data to confirm findings.
Weather Forecasting: Combines real-time observations, physics principles, and computer models. These models are validated by successfully reproducing past weather and accurately predicting future conditions.
2. Core Concepts: Weather, Climate, and Meteorology
Weather: The atmosphere's state right now in a specific location.
Key Weather Elements:
Air temperature
Air pressure
Humidity (water vapor amount)
Clouds
Precipitation (rain, snow, etc.)
Visibility (how far one can see)
Wind (direction and speed)
Climate: The long-term average and extreme patterns of weather events over extended periods (e.g., 30 years).
Meteorology: The scientific study of the atmosphere and its phenomena (weather events), with roots traced back to Aristotle.
Key Distinction: Weather changes rapidly (minutes to hours); climate evolves slowly (decades to centuries). Both are governed by atmospheric physics and chemistry.
3. Composition of the Atmosphere
Major Dry-Air Gases (near surface): (These amounts are relatively stable)
Nitrogen (\text{N}_2): ~78.08\% (most abundant)
Oxygen (\text{O}_2): ~20.95\% (essential for life)
Argon (\text{Ar}): ~0.93\%
Trace gases: Neon, Helium, Xenon (in very small quantities).
Variable Gases (amounts change by location/time):
Water Vapor: Varies from 0\%
to 4\%
by volume. It is a crucial greenhouse gas and exchanges energy as latent heat during phase changes.
Carbon Dioxide (\text{CO}_2): ~0.04\%
(~400 ppm) and rising due to fossil fuel burning and deforestation. It's a key greenhouse gas.
Other Important Greenhouse Gases: Methane (\text{CH}4), Nitrous Oxide (\text{N}2\text{O}), Ozone (\text{O}_3). These also trap heat.
Ozone (\text{O}_3):
Stratospheric Ozone (high up): Forms a protective layer, absorbing harmful UV radiation from the Sun.
Surface Ozone (low down): A harmful pollutant, contributing to photochemical smog.
Aerosols & Pollutants:
Aerosols: Tiny solid or liquid particles suspended in the air (e.g., dust, smoke, soot, sulfates). They affect visibility, air quality, and cloud formation.
Pollutants: Harmful gases (e.g., Nitrogen Dioxide (\text{NO}2), Carbon Monoxide (CO), Sulfur Dioxide (\text{SO}2)) that impact air quality and human health.
4. Vertical Structure and Layers of the Atmosphere
General Structure: The atmosphere is thin; ~99\%
of its mass is within the lowest ~30\text{ km}.
Pressure & Density: Both decrease rapidly with increasing height because there are fewer air molecules above.
Sea Level Pressure: Average is ~1013.25\text{ mb}.
Pressure approximately halves every ~5.5\text{ km}; by 50\text{ km}, it's ~1\text{ mb}.
Temperature Layers (from ground up):
Troposphere: The lowest layer (surface to ~11\text{ km}). Temperature generally decreases with height (average lapse rate ~6.5^\circ\text{C} \text{ per } 1000\text{ m}). Most weather occurs here.
Tropopause: The boundary between the troposphere and stratosphere; temperature change is minimal.
Stratosphere: Above the tropopause (~11\text{ km} to 50\text{ km}). Temperature increases with height (a temperature inversion) due to ozone absorbing UV radiation.
Mesosphere: Above the stratosphere (~50\text{ km} to 85\text{ km}). Temperature decreases with height, reaching the coldest atmospheric temperatures at its top (mesopause).
Thermosphere: Above the mesosphere (~85\text{ km} to 500\text{ km}). Features very high temperatures due to solar energy absorption, but its extremely low density means it would feel cold.
Exosphere: The outermost layer, where the atmosphere gradually fades into space. Light gases (hydrogen, helium) can escape from here.
Other Key Regions:
Homosphere: The lower atmosphere (~0\text{ to } 80\text{ km}) where major gases are well-mixed and uniform.
Heterosphere: The upper atmosphere where gases separate by molecular weight, with lighter gases dominating at higher altitudes.
Ionosphere: An electrically charged region (within the mesosphere and thermosphere) containing ions and free electrons, important for reflecting radio waves.
Dynamic Markers: The tropopause and jet streams mark regions of rapid atmospheric changes and steer weather systems.
5. Atmospheric Energy, Motion, and Weather Systems
Latent Heat: Energy absorbed or released during water phase changes (e.g., evaporation, condensation, freezing, melting). It is a major energy source that powers storms.
Greenhouse Effect: A natural process where specific atmospheric gases (mainly water vapor and carbon dioxide (\text{CO}_2)) trap outgoing infrared energy radiated from Earth, warming the surface and maintaining habitable temperatures.
Weather Maps & Pressure Systems:
Isobars: Lines on weather maps connecting points of equal atmospheric pressure. Winds tend to flow parallel to isobars.
High-Pressure Centers (H): Typically bring clear skies. In the Northern Hemisphere, winds blow clockwise and outward.
Low-Pressure Centers (L): Often bring clouds and precipitation. In the Northern Hemisphere, winds blow counterclockwise and inward.
Fronts (Boundaries between Air Masses):
Cold Front: (Blue line with triangles) Cold air pushes into warm air, often causing abrupt temperature drops, heavy precipitation, and thunderstorms.
Warm Front: (Red line with half-circles) Warm air gently rises over cooler air, usually bringing widespread, lighter precipitation over a longer duration.
Occluded Front: (Purple line with alternating triangles and circles) Forms when a cold front overtakes a warm front, lifting the warm air mass from the surface.
Mid-Latitude Weather Systems: Large systems (like cyclonic storms) in the middle latitudes are primarily steered by upper-level winds, such as jet streams.
6. Climate Change and Human Impact
Rising Carbon Dioxide (\text{CO}_2): Atmospheric concentrations have increased from ~280\text{ ppm}
(pre-industrial) to ~400-410\text{ ppm}
today, rising ~0.5\%
per year (recorded at Mauna Loa). This rise, largely from fossil fuels and deforestation, drives long-term climate change.
Ozone Depletion: Stratospheric ozone, which shields Earth from UV, is depleted by human-made CFCs (chlorofluorocarbons). This leads to seasonal "ozone holes" (e.g., over Antarctica in spring).
Climate Forcing: Human activities (e.g., greenhouse gas emissions, aerosol pollution, land-use changes) significantly alter the atmosphere's composition, causing long-term shifts in climate.
7. Key Terms and Definitions
atmosphere: Earth's protective layer of air.
weather: Current state of the atmosphere.
weather elements: Temperature, pressure, humidity, clouds, precipitation, visibility, wind.
climate: Long-term average weather.
meteorology: Study of atmosphere and weather.
middle latitudes: Regions between 30^\circ
and 60^\circ
latitude.
middle-latitude cyclonic storm: Large low-pressure storm with fronts.
hurricane: Strong tropical storm over oceans (>74\text{ mph}
winds).
thunderstorms: Storms with lightning, thunder, heavy rain.
tornadoes: Violent, spinning air columns from storms to ground.
wind: Air movement due to pressure differences.
wind direction: Where wind comes from.
wind speed: How fast wind moves.
front: Boundary between air masses.
outgassing: Gases released from Earth's interior.
nitrogen (\text{N}_2): ~78\%
of dry air, unreactive.
oxygen (\text{O}_2): ~21\%
of dry air, essential for life.
lapse rate: How temperature changes with height (usually drops).
temperature inversion: Temperature rises with height (traps pollutants).
radiosonde: Balloon tool measuring temperature, humidity, pressure.
troposphere: Lowest layer; most weather, temperature drops with height.
stratosphere: Layer above troposphere; ozone heats it, temperature rises with height.
tropopause: Boundary between troposphere and stratosphere.
mesosphere: Above stratosphere; temperature drops, coldest layer.
thermosphere: Outermost layer; very hot but thin air.
ionosphere: Electrified region, important for radio waves.
ozone (\text{O}_3): Protects from UV (stratosphere), pollutant (surface).
aerosols: Tiny airborne particles (dust, smoke).
pollutants: Harmful substances in air (e.g., Nitrogen Dioxide (\text{NO}2), Carbon Monoxide (CO), Sulfur Dioxide (\text{SO}2)).
Nitrogen dioxide (\text{NO}_2): Gas causing smog/acid rain.
Carbon monoxide (CO): Toxic gas from burning fuels.
Sulfur dioxide (\text{SO}_2): Gas causing acid rain/breathing issues.
CO$_2$ cycle: Natural exchange of carbon dioxide.
greenhouse gases: Gases that trap heat (e.g., \text{CO}_2), water vapor).
Mauna Loa: Observatory tracking \text{CO}_2$$
increase.
Dobson Units: Unit for measuring ozone amount.
ozone hole: Seasonal thinning of ozone layer (Antarctica).
exosphere: Outermost layer where gases escape.
homosphere: Lower, well-mixed atmosphere.
heterosphere: Upper atmosphere where gases separate.
jet streams: Fast high-altitude winds steering weather.
isobars: Lines of equal pressure on maps.
storms: Disturbed atmospheric state with strong winds/precipitation.