MARÉS

Tides & gravity

• Gravity from the Moon and Sun — their combined influence on the tides.
• Moon phases, spring and neap tides — why the difference between high and low water changes through the month.
• Semidiurnal tides — two high and two low waters within a lunar day.
• Earth’s rotation, the Moon’s orbit and the lunar day — about 24 hours and 50 minutes; why tide times shift from day to day.
• Tidal range and tidal currents — the connection between changing water levels and flowing water.
• The Moon’s elliptical orbit and local water depth — why tides vary from place to place; the influence of coastlines and the shape of the seabed, known as bathymetry.

Waves & currents

• Energy transfer from wind to water — how wind-driven surface waves form.
• Wave height — the influence of wind speed, wind duration and the distance over which wind blows across water, known as fetch.
• Swell from the open ocean — how waves reach the coast from distant source regions; comparison with a more enclosed sea.
• Energy transport and water transport — waves carry energy; currents transport water and can modify waves.

Experienced in water

• Buoyancy, water pressure and movement — the physics connected with swimming and exploring in water.

Sun angle & solar energy

• The angle of incoming sunlight — how the same radiant power is spread over a smaller or larger surface area.
• Irradiance and latitude — why a higher Sun can mean more solar power per square metre.
• Time of day and the path through the atmosphere — how solar elevation changes the distance light travels through air and the amount of attenuation.

Light, sky colour & ultraviolet

• Wavelength and ultraviolet radiation — the distinction between UVA, UVB and UVC.
• Absorption and atmospheric filtering — the role of ozone and other atmospheric constituents; solar UVC and most UVB do not reach the ground.
• Scattering and the blue sky — air molecules scatter shorter wavelengths of visible light more strongly than longer wavelengths.
• Reflection, direct and diffuse radiation — light and UV can arrive from different directions through the sky and from reflective surfaces.
• Transmission through clouds and water — why cloud cover, shade or being in the water do not eliminate ultraviolet radiation.

Above and below the surface

• Refraction and colours underwater — how light and perception change at the water’s surface and beneath it.
• The Sun’s path, Earth’s rotation and twilight — the cycle of day and night and the brief transitions near the equator.
• Moonlight, darkness and orientation — exploring connections between coast and sky after daylight.

Heat, water & clouds

• Solar energy and ocean warming — the sea as a source of heat and moisture for the atmosphere.
• Evaporation and humidity — the transition from liquid water to water vapour.
• Convection and the cooling of rising air — how heat and moisture are transported upwards.
• Condensation and latent heat — the formation of cloud droplets and the energy released in the process.
• Atmospheric instability, storm clouds and rain — how moisture, uplift and instability allow cumulonimbus clouds and heavy showers to develop.

Breezes & tropical circulation

• Sea and land breezes — alternating local air movements between land and sea.
• Convergence and rising air — how winds coming together can lift air.
• The Intertropical Convergence Zone — where trade winds from the two hemispheres meet; its seasonal migration and connection with tropical rainfall patterns.