Insolation & Temperature (Hess Ch. 4 Notes)

Solar Energy and Electromagnetic Radiation

The Sun is the ultimate energy source for Earth’s weather and climate.
Energy travels as electromagnetic radiation (EMR):
- Shortwave radiation (UV, visible light, some infrared) from the Sun.
- Longwave radiation (infrared/heat) emitted back from Earth.
Atmosphere is largely transparent to visible light but absorbs some UV and IR.

Radiation – Transfer of energy by EM waves (e.g., Sun → Earth).
Absorption – Atmosphere or surface absorbs radiation, converting it to heat.
Reflection – Radiation bounces back without absorption (e.g., clouds, ice).
Scattering – Radiation deflected in many directions (sky looks blue).
Transmission – Radiation passes through atmosphere (e.g., visible light).
Conduction – Heat transfer through direct contact (molecules → molecules).
Convection – Heat transfer by rising warm air and sinking cool air.
Advection – Horizontal transfer of heat by wind (e.g., sea breeze).
Adiabatic Cooling/Warming – Temperature change due to air expansion (cooling as it rises) or compression (warming as it sinks), without heat exchange.
Latent Heat – Energy absorbed/released during phase changes of water (melting, evaporation, condensation).

Certain gases (CO₂, CH₄, H₂O vapor) absorb Earth’s longwave IR radiation and re- radiate it back.
This traps heat and keeps Earth warmer than it would be (~ riangle T \,\approx \,33^{\circ}\mathrm{C} warmer).
Natural and necessary for life, but human activities have enhanced the effect → global warming.

Latitude:
- Equator → receives most direct, concentrated sunlight.
- Poles → sunlight spreads over larger area, lower angle, less energy.
Season:
- Caused by Earth’s axial tilt (\phi = 23.5^{\circ}), not distance from Sun.
- Summer hemisphere → more direct rays, longer days.
- Winter hemisphere → less direct rays, shorter days.
Atmosphere modifies insolation through absorption, reflection, scattering, reducing surface energy.

Specific heat – energy required to raise temperature of a substance.
- Water has high specific heat → heats/cools slowly.
- Land has low specific heat → heats/cools quickly.
Other factors:
- Water is transparent (heat distributed through depth).
- Mixing of water spreads heat.
- Evaporation cools water surfaces.
Implications for climate:
- Continental climates (inland): Larger temperature swings, hotter summers, colder winters.
- Maritime climates (coastal): Milder, smaller annual temperature range.

Insolation – Incoming solar radiation received at Earth’s surface.
Greenhouse Gases – Atmospheric gases (CO₂, H₂O vapor, CH₄) that trap heat.
Latent Heat – Energy absorbed/released during phase changes of water without changing temperature.
Albedo – Reflectivity of a surface (high for ice/snow, low for dark soil/ocean).

Links to energy balance and radiative transfer in atmospheric science.
Radiative forcing: greenhouse gases modify outgoing longwave radiation, altering surface temperature.
Real-world relevance: understanding climate zones, weather patterns, and the basis for climate change discussions.

Human activities (fossil fuel use, deforestation, agriculture) have enhanced the greenhouse effect, contributing to global warming.
Implications for policy: energy choices, emissions reductions, adaptation strategies, climate justice.
Practical climate considerations: planning for extreme temperature swings in continental interiors and designing infrastructure for maritime climates.

Latent Heat (phase change): Q = mL
- Q: heat transferred during a phase change, m: mass, L: latent heat of fusion/vaporization.
Specific Heat (definition and relation): Q = m c \Delta T
- Q: heat added or removed, m: mass, c: specific heat capacity, \Delta T: change in temperature.
Axial Tilt (seasonal cause): \phi = 23.5^{\circ}
Greenhouse Temperature Increase (typical estimate): \Delta T \approx 33^{\circ}\mathrm{C}
Albedo – qualitative descriptor: high for ice/snow, low for dark soil/ocean (no fixed numeric value provided in transcript).