HKDSE Geography/E2/Precipitation

Classification
Types of precipitation include:
 * Rain
 * Hail
 * Sleet (not present in Hong Kong)
 * Snow (not present in Hong Kong)

General Steps

 * 1) Warm air converges, rises up, expands to form uprising air currents.
 * 2) As warm air rises, it falls by 6 degrees Celsius per 1000 m. Relative humidity increase.
 * 3) At the condensation level, relative humidity reaches 100%, or dew point. The air is said to be saturated.
 * 4) Excess water vapour condenses on condensation nuclei. Water droplets form.
 * 5) Water droplets accumulate to form clouds.
 * 6) When the clouds are too heavy to support, the droplets fall as rain.
 * 7) Sometimes accompanied by thunderstorms or lightning.

Three Types of Rain
For each of the following types of rain, warm air rises for different reasons.

Frontal Rain

 * A cold front occurs when a warm air mass and a cold air mass meet.
 * The warm air mass is forced up by the cold air mass.