Weather and Climate Study Notes

Introduction to the Atmosphere

  • Definition: The atmosphere is a thin layer of gases surrounding the Earth.
  • Composition of Air:
    • Water vapor: Water in gaseous form.
    • Abundant Gases:
    • Nitrogen (78%)
    • Oxygen (21%)

Layers of the Atmosphere

  • Five Layers (from surface to space):
    1. Troposphere
    2. Stratosphere
    3. Mesosphere
    4. Thermosphere
    5. Exosphere
  • Distinguishing Layers: Different layers are distinguished by changes in temperature.
  • Weather Events: Most weather occurs in the troposphere.
  • Stratosphere Temperature: Temperature increases with altitude in the stratosphere because of the ozone layer absorbing solar radiation.
  • Ozone Layer Location: Found in the stratosphere.

Air Pressure

  • Definition: Air pressure is the force exerted by a column of air on the air or surface below.
  • Altitude Relationship: As altitude increases, air pressure decreases.
  • Measurement Instrument: A barometer is used to measure air pressure.

Heat Transfer

  • Methods of Heat Transfer:
    1. Radiation: Transfer of heat by electromagnetic waves (e.g. sunlight).
    2. Conduction: Heat transfer through particle collisions (e.g. a pan on a hot stove).
    3. Convection: Heat transfer through the movement of particles within fluids (e.g. boiling water).

Wind Formation

  • Definition of Wind: Horizontal movement of air from areas of high to low pressure.
  • Causes of Wind: Differences in air pressure create wind.
  • Measuring Instruments:
    • Anemometer: Measures wind speed.
    • Wind Vane: Measures wind direction.
  • Coriolis Effect: The Earth's rotation causes winds to curve.
  • Global Winds: Steady winds over long distances include:
    • Doldrums
    • Trade Winds
    • Prevailing Westerlies
    • Polar Easterlies
    • Jet Streams

Weather Concepts

  • Weather Definition: Current atmospheric conditions.
  • Factors Affecting Weather:
    1. Temperature
    2. Humidity
    3. Relative Humidity
    4. Air Pressure
    5. Wind
    6. Cloudiness

Clouds and Precipitation

  • Cloud Formation: Water droplets or ice crystals suspended in the atmosphere.
  • Types of Clouds:
    • Cumulus: Fluffy, cotton ball-like appearance.
    • Cumulonimbus: Produces thunderstorms.
    • Stratus: Flat, gray clouds covering the sky.
    • Nimbostratus: Larger stratus clouds that produce precipitation.
    • Cirrus: Wispy clouds resembling feathers.
  • Precipitation: Water falling from clouds can take various forms:
    • Rain
    • Snow
    • Sleet
    • Hail
    • Freezing Rain

Air Masses and Fronts

  • Air Mass Definition: A large body of air with uniform temperature, humidity, and pressure.
  • Air Mass Types:
    • Continental: Dry air masses forming over land.
    • Maritime: Wet air masses forming over the ocean.
    • Polar: Cold air masses.
    • Tropical: Warm air masses.
  • North American Air Masses:
    • Arctic
    • Continental Polar
    • Continental Tropical
    • Maritime Polar
    • Maritime Tropical
  • Fronts: Boundaries between two air masses.
    • Cold Front: Moves cold air towards warm air, often causing thunderstorms.
    • Warm Front: Warm air moves toward colder air, leading to steady rain or snow.
    • Occluded Front: Fast-moving cold front catches up with a warm front, producing precipitation.
    • Stationary Front: Boundary stalls, causing prolonged rain or snow.

Storms and Severe Weather

  • Thunderstorms: Rain storms accompanied by thunder and lightning, typically form within cumulonimbus clouds.
  • Lightning: Electricity discharge during storms.
  • Hurricanes: Intense storms with winds over 119 km/h.
  • Blizzards: Snowstorms marked by low temperatures and high winds.
  • Tornadoes: Violently rotating columns of air contacting the ground, forming mainly in the Central U.S.

Meteorological Tools

  • Meteorologist: Scientists who study and predict weather.
  • Radiosonde: Instruments used in weather balloons for data collection.
  • Isotherm: Lines on weather maps connecting points of equal temperature.
  • Isobar: Lines on weather maps connecting points of equal pressure.

Climate Concepts

  • Climate Definition: Long-term average weather conditions of a region.
  • Latitude: Position relative to the equator, important for climate:
    • Equator: 0°
    • Poles: 90°
  • Temperature Variation by Latitude: Equator generally warmer due to direct sunlight.
  • Rain Shadow: Low rainfall area on the downwind side of mountains.
  • Heat Dynamics: Land heats and cools faster than water.

Seasonal Changes

  • Cause of Seasons: Changes in solar radiation received throughout the year.
  • Solstices: Longest and shortest days of the year (first days of summer/winter).
  • Equinoxes: Equal day and night duration (first days of spring/autumn).
  • El Niño: Ocean-atmosphere cycle in the tropical Pacific that affects weather patterns, characterized by weakened trade winds.