Geo Notes Midterm

Examination Overview

  • Exam Date: Next week on October 6.

Organization of Topics

Theme 1: Portraying the Earth

  • Lecture 1: Introduction to Physical Geography

  • Reading: McKnight Chapter 2

  • Labs: Labs 1, 2, and 3

  • Key Topics:

    • Map scales

    • Isolines

    • Contour lines

    • Topographic profiles (vertical and horizontal scales)

    • GIS Introduction

Theme 2: Introduction to Earth Systems

  • Lectures: 1 and 2

  • Reading: McKnight Chapter 1

  • Labs: Labs 2 and 4

  • Key Topics:

    • Earth-Sun Relations

    • Solar Angles

    • Insolation

Theme 3: Atmosphere and Temperature

  • Lectures: 3 to 10

  • Reading: McKnight Chapters 3 to 6

  • Labs: Labs 4 and 5

  • Key Topics:

    • Temperature Patterns

    • Atmospheric Obstruction

    • Air Pressure

    • Wind

Theme 1: Portraying the Earth

Size and Shape of the Earth

  • The Earth is considered an oblate spheroid.

    • Equatorial Diameter: 12,756 km (7,927 mi)

    • Polar Diameter: 12,714 km (7,900 mi)

    • Comparison: The diameter of our sun is 1,392,000 km (865,000 mi), equivalent to 109 Earths.

Defining Locations on Earth: Latitude and Longitude

  • Latitude (North/South): Remains at fairly consistent distances.

  • Longitude (East/West): Physical distance between intervals varies significantly between the poles and the equator.

    • World Time Zones: Defined using 15° longitude increments:

    • Calculation: 360ext°ext÷24hrs=15ext°360^ ext{°} ext{ ÷ 24 hrs = 15}^ ext{°}

  • Degrees are identified as:

    • 0º, 15º, 30º, 45º, etc.

Types of Scales in Cartography

  • Verbal Scale: Expressed in words (e.g., "One inch represents one mile").

  • Graphic Scale: Shown as a bar graph indicating distance. Measurement can be done with a ruler or paper.

  • Fractional/Representative Scale: (e.g., 1:50,000 or 1/50,000)

    • Meaning: 1 unit on the map equals 50,000 units in reality.

  • Note: Scales can use any unit as long as they are consistent.

Isolines

  • Definition: Lines connecting points of equal value on a map.

  • Characteristics: Points on either side of an isoline do not equal the isoline value.

Contour Line Map Terms

  • Contour Interval: Difference in elevation between two contour lines.

  • Index Contour: A wider, darker contour line indicating elevation.

  • Depression Contours: Depicted by closed contour lines with hachures leading into the depression.

  • Local Relief: The difference between the highest and lowest elevation points.

Theme 2: Introduction to Earth Systems

Earth-Sun Relations

  • Circle of Illumination: The edge that separates daylight from nighttime.

  • Apparent Movement of the Sun: Resulting from the Earth's rotation.

Reasons for the Seasons

  • Identified by special days of the year such as equinoxes and solstices.

    • Declination of the Sun & Solar Angle: Critical in understanding seasonal changes.

Equinoxes and Solstices




  • Defined as follows:


    Event

    24 Hours of Daylight

    24 Hours of Darkness

    12 Hours of Daylight + Darkness

    90-degree Angle of Incidence



    March Equinox

    No

    No

    Yes

    Equator



    June Solstice

    North of Arctic Circle

    South of Antarctic Circle

    No

    Tropic of Cancer



    September Equinox

    No

    No

    Yes

    Equator



    December Solstice

    South of Antarctic Circle

    North of Arctic Circle

    No

    Tropic of Capricorn








    Seven Special Parallels






    • Key latitudes include:

      • North Pole (90° N)

      • Arctic Circle (66.5° N)

      • Tropic of Cancer (23.5° N)

      • Equator (0°)

      • Tropic of Capricorn (23.5° S)

      • Antarctic Circle (66.5° S)

      • South Pole (90° S)

    Solar Angle

    • Solar Declination: The latitude of maximum solar position during noon.

      • Varies by 47° throughout the year between the Tropics.

    • Angle of Incidence: Determines solar energy intensity received by Earth's surface; maximum when the Sun is directly overhead.

    Theme 3: Temperature, Pressure, and Atmosphere

    Heat Energy

    • Defined as the total kinetic energy from the internal motion of atoms and molecules in a substance.

      • Dependent Factors:

      • Speed of molecules

      • Number of molecules (mass)

      • Type of molecules

    • Temperature: A measure of average internal motion not dependent on size/type; higher temps mean greater molecular motion.

    Heat Transfer Mechanisms

    • Radiation: Energy is emitted as electromagnetic waves.

      • An increase in radiation absorbed warms the object; a decrease cools it.

    • Stefan-Boltzmann Law: The emitted power of a blackbody object is given by: P=extσAT4P = ext{σ}AT^4

      • Where:

      • PP = Power

      • σσ = Stefan-Boltzmann constant

      • AA = Surface area in m2m^2

      • TT = Temperature in Kelvins (K)

    • Greenhouse Effect: Mechanism increasing Earth’s surface temp beyond equilibrium radiative temperature.

    Insolation

    • Definition: Incoming Solar Radiation; the rate at which solar energy strikes a surface.

      • Measured as intensity: amount of energy received over time in a specific area.

    • Solar Constant: The total solar energy received at Earth's surface averaged over a year is 1370extW/m21370 ext{W/m}^2.

      • Average insolation at surface is reduced by various factors: angle of incidence, length of day, atmospheric obstruction.

      • Average solar radiation at the surface is ¼ of the solar constant: 342extW/m2342 ext{W/m}^2.

    Atmospheric Obstruction

    • Factors impacting insolation include clouds, smoke, and gas particles.

    • Impact of Particle Size: Larger particles preferentially scatter longer wavelengths (reds), while aerosols (dust) scatter shorter wavelengths.

    • The Angle of Incidence is critical, influencing the average daily insolation.

    Earth's Radiation Balance

    • Solar absorption must balance with emissions to maintain constant temperature.

      • Emission Characteristics:

      • Sun emits short-wave radiation (< 4 µm).

      • Earth emits long-wave radiation (> 4 µm).

    • Emission values are:

      • 342extW/m2342 ext{W/m}^2 absorbed,

      • 240extW/m2240 ext{W/m}^2 emitted back to space.

    Surface Reflectance

    • Surface Albedo (α): Measure of reflectivity of a surface; values range from 0 to 1 (or percentage).

    Heat Transfer Mechanisms in the Atmosphere

    Convection

    • Process: Warm air rises, cool air sinks, with surface air warmed indirectly by the Sun.

    • This results in constant convective activity transferring heat.

    • Latent Heat: Evaporation cools the surface, while condensation warms the atmosphere; significant in heat transfer.

    Vertical Structure of the Atmosphere

    • Atmospheric Layers:

      1. Troposphere

      2. Stratosphere

      3. Mesosphere

      4. Thermosphere

    • Each layer has unique temperature characteristics with altitude variation.

    Temperature Patterns

    • Important factors influencing global temperature:

      • Latitude

      • Land-water contrasts

      • Ocean currents

      • Wind patterns

      • Altitudes

    Atmospheric Pressure

    • Standard air pressure at sea level: 1 atm = 101.3 kPa = 1013 mb = 14.7 psi.

    • High pressure is considered greater than 1013 mb, low pressure is less.

    • Falls approximately by a factor of 2 every 5.6 km of altitude.

    Global Circulation

    1. Pressure Gradient Force

    2. Coriolis Effect

    3. Friction

    • These forces dictate the atmospheric circulation patterns.

    Coriolis Effect

    • Definition: Refers to the deflection of objects moving across Earth’s surface due to rotation.

    • Affects wind direction far above 3300 feet (1000 meters), deflecting to the right in the Northern Hemisphere and left in the Southern Hemisphere.

    Anticyclones vs. Cyclones

    • Anticyclones: High-pressure systems; winds diverge clockwise.

    • Cyclones: Low-pressure systems; winds converge counterclockwise.

    Atmospheric Disturbances

    Cyclone Characteristics

    • Features include:

      • Surface air convergence, unstable atmosphere, rising air, and low surface pressure.

    Global Circulation: Jet Streams

    • Fast-moving air currents in the atmosphere, spanning thousands of kilometers, dividing cold and warm air.

    • Rossby Waves: Undulations in jet stream affecting weather patterns, taking 10-14 days to traverse the US.

    Ideal Gas Law

    • Equation: P[extPa]=R⋅ρ[extkg/m3]⋅T[K]P[ ext{Pa}] = R · ρ [ ext{kg/m}^3] · T[K] where R = 287 extJkg−1extK−1ext{J kg}^{-1} ext{K}^{-1}.

    • Examines relationships between pressure, temperature, and density; revealing interactions between variables in atmospheric science.

    Implications for Climate Change

    • Warm air's capacity for water vapor increases significantly with temperature; higher saturation vapor pressure leads to greater potential water content in warmer environments.

    • Evaporative Cooling: Less effective near saturation, relevant in climate change considerations.