Precipitation and evapotranspiration - Fundamentals of the Physical Environment - page 82

Sublimation/Condensation

Precipitation

Ice cap

P recipitation

Evaporation
of rainfall

Advection of moisture
to maintain precipitation

Precipitation

Runoff

Groundwater
flow

Evaporation

Evapotranspiration

Sea, lake or
channel

Figure 5.1 Schematic representation of the hydrological cycle, showing the main flows of water to and from the atmosphere.

Table 5.1 Types of precipitation

Type Characteristics Typical amount

Dew Deposited on surfaces, especially vegetation; hoar frost when frozen 0·1-1·0 mm per night

Fog-drip Deposited on vegetation and other obstacles from fog; rime when frozen Up to 4 mm per night

Drizzle Droplets under 0·5 mm in diameter 0·1-0·5 mm per hour

Rain Drops over 0·5 mm in diameter, usually 1-2 mm Light, under 2 mm per hour;

heavy, over 7 mm per hour

Hail Roughly spherical lumps of ice 5-50 mm or more in diameter, often Highly variable

showing a layered structure of opaque and clear ice in cross-section

Snowflakes Clusters of ice crystals up to several centimetres across Variable

Granular snow Very small flat opaque grains of ice; solid equivalent of drizzle Light, under 1 mm per hour

Snow pellets Opaque pellets of ice 2-5 mm in diameter falling in showers Variable

(graupel or soft hail)
Ice pellets

Clear ice encasing a snowflake or snow pellet

Sleet (UK) Mixture of partly melted snow and rain

Sleet (US) Frozen rain or drizzle drops