Geography - ELSS

The water balance (budget)

The balance between inputs and outputs. Affects how much water is stored in a system. General water balance in the UK shows seasonal patterns e.g. In wet seasons, precipitation is higher than evapotranspiration - creating a water surplus

Water balance formula

Precipitation(P) = stream flow(Q) + evapotranspiration(E) ± changes in storage (S)

Orographic rain/Relief Rain

1. Dry parcel of air

2. Wind moves the parcel of air over land

3. Mountains force the parcel to rise up over it

4. Air cools as it reaches its dew point

5. Air continues to cool at saturated lapse rate + clouds form

6. Air then descends, warming the air and creates stable, dry conditions.

Types of clouds - Low

Nimbostratus (rain maker), cumulus, stratocumulus, stratus

Types of clouds - Middle

Altocumulus, altostratus

Types of clouds - HIgh

Cirrus, cirrocumulus, cirrostratus

All 3?

Cumulonimbus - rain maker cloud

Frontal rain formation

Frontal rainfall occurs when two air masses meet at a front, forcing warm air to rise over cooler, denser air.

• Warm front:

  • Warm air gradually rises over cold air

  • Slow uplift → stratus clouds → prolonged, steady rain

• Cold front:

  • Cold air undercuts warm air sharply

  • Rapid uplift → cumulonimbus clouds → heavy, short-lived rainfall

Key process:
Rising air cools → condensation → cloud formation → precipitation

Adiabatic temperature changes

Temperature changes in a parcel of air due to expansion or compression, without heat exchange with the surrounding environment.

• As air rises, pressure decreases → air expands and cools (adiabatic cooling)

• As air descends, pressure increases → air compresses and warms (adiabatic warming)

Diurnal changes vs seasonal changes

The global carbon cycle

The global carbon cycle involves the movement of carbon between atmosphere, terrestrial biosphere, oceans and geological reservoirs with quantified fluxes - measured in Gigatonnes