Atmosphere and Weather

1. Layers of the Atmosphere

• Closest to Earth, where all weather occurs

• Contains 80% of atmospheric mass (air, clouds, water vapor)

• Temperature decreases with altitude

• Mount Everest (8.8 km) is within this layer

• Airplanes and jet aircraft fly in the upper troposphere

Tropopause

• Boundary between Troposphere and Stratosphere

• Temperature & pressure increase compared to the Troposphere

Stratosphere (12-50 km)

• Ozone layer (O₃) absorbs UV radiation, protecting life on Earth

• Jet streams (strong air currents) are present

• Some aircraft and weather balloons fly here

• Temperature increases with altitude

Stratopause

• Transition layer between Stratosphere and Mesosphere

• Temperature drops

Mesosphere (50-85 km)

• Coldest layer (-90°C at the top)

• Protects Earth by burning meteors

• Noctilucent clouds (rare clouds made of ice) form here

Thermosphere (85-600 km)

• Absorbs high-energy radiation (X-rays, UV rays)

• Contains the Ionosphere, where charged particles create auroras

• Space stations (e.g., ISS) orbit in the lower Thermosphere

Exosphere (600+ km)

• Outermost layer, merges with space

• Satellites orbit here

• Very thin air, mostly hydrogen and helium

Kármán Line (100 km above Earth)

• Boundary between atmosphere and outer space

Magnetosphere

• Protects Earth from harmful solar flares and cosmic radiation

• Forms when Earth's magnetic field interacts with solar wind

• When solar wind enters the poles, it creates auroras:

o Aurora Borealis (Northern Hemisphere)

o Aurora Australis (Southern Hemisphere)

• Strong solar storms disrupt communication and electricity

Importance of the Atmosphere

• Shields from UV radiation & cosmic rays

• Regulates temperature & weather

• Prevents space debris from reaching Earth

• Supports life (oxygen, CO₂ for photosynthesis)

2. Atmospheric Circulation
Earth’s Movements

• Rotation (spinning on axis, 23h 56m) → causes:

o Day & night

o Tides (high & low)

o Coriolis Effect (wind & ocean currents curve)

o Time zones

o Flattened poles due to centrifugal force

o Seasons & climate variations

o Seasonal constellations

o Leap years

What Causes Wind?

• Temperature differences: Warm air rises, cool air sinks

• Pressure differences: Air moves from high to low pressure

• Rotation: Coriolis effect deflects winds right in the Northern Hemisphere, left in the
Southern Hemisphere

• Altitude: Higher = lower pressure & cooler temperatures

3. Breezes (Local Wind Systems)

• Land heats up faster → warm air rises → low pressure

• Cool air from the sea (high pressure) moves in → Sea Breeze

• Land = Warm, Low Pressure

• Sea = Cool, High Pressure

Land Breeze (Nighttime)

• Land cools faster than water → high pressure over land

• Warm air over sea rises → low pressure over sea

• Cool air from land moves in → Land Breeze

Mountain Breeze (Nighttime)

• Mountain slopes cool faster, creating high pressure

• Cold air sinks into valleys → Mountain Breeze

Valley Breeze (Daytime)

• Sun warms valley floor → warm air rises → low pressure

• Cool air from mountain slopes moves in → Valley Breeze

Formation of Breezes

1. Unequal heating of land & water

3. Air moves from high to low pressure

4. Monsoons (Seasonal Winds)

• From Australia (Summer)

• Warm, moist air → heavy rain

Amihan (Northeast Monsoon, Nov–Feb)

• From China/Siberia (Winter)

• Cool, dry air → light rain

5. Global Winds & Wind Belts

• Hadley Cell → Trade Winds (East to West)

• Ferrel Cell → Westerlies (West to East)

• Polar Cell → Polar Easterlies (East to West)

Pressure Zones

• Doldrums → Low pressure, weak winds (near Equator)

• Horse Latitudes → High pressure, weak winds (30° N/S)

6. Water Cycle
Stages

1. Evaporation: Sun heats water → water vapor

2. Condensation: Vapor cools → clouds form

3. Precipitation: Water falls (rain, snow, etc.)

4. Runoff & Seepage: Water returns to oceans, lakes, or underground

Forms of Precipitation

• Rain, drizzle, snow, sleet, hail, glaze

Importance of Water Cycle

• Distributes freshwater

• Sustains ecosystems & agriculture

• Recharges groundwater

7. Acid Rain
• pH < 7 (acidic) → caused by factories & fossil fuels

• Harms water, soil, forests, buildings, animals, humans

8. Cloud Seeding (Artificial Rain)

• Airborne Seeding: Short-lasting, potential pollutants

• Ground Seeding: Requires clouds, wind direction, temperature

Purpose

• Increases rainfall in drought areas

• Boosts freshwater supply for agriculture & dams

• Prevents wildfires & regulates climate

Key Takeaways
Atmosphere protects life, controls weather, and shields from harmful radiation
Air moves due to temperature, pressure, altitude, and Earth’s rotation
Breezes & monsoons depend on pressure & seasonal changes
Water cycle ensures climate stability, water distribution, and sustains life
Human activities like pollution cause acid rain & climate change
Cloud seeding can be used for weather control