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  1. Affects rain formation in such as way that places with high humidity are likely to experience higher rainfall than those with low humidity.
  2. Regulates the heat loss from the earth’s surface by absorbing terrestrial radiation (process in which the earth gives off heat into the atmosphere).
  3. It affects sensible temperature in that the higher the humidity the more we experience sensible temperature.


-The forms in which the earth’s surface receives moisture.

  1. Snow

Solid precipitation formed when tiny water droplets freeze and form ice crystals.

The crystals may fuse to form flakes.

  1. Sleet

-Precipitation which is a mixture of rain and snow.

  1. Hail

Roughly spherical lumps of ice formed when super cooled cloud droplets mould themselves around ice crystals before cooling. It destroys crops life and house roofs.

  1. Dew

-Precipitation consisting of water droplets formed on cold surfaces at night e.g. iron roofs and glass blades.

How It’s Formed

  • In a clear night there is a high ground radiation.
  • Temperature of the earth’s surface fall below dew point (temperature at which air being cooled becomes saturated).
  • Excess water condenses on cold surfaces.
  1. rain

-Precipitation consisting of water drops/droplets formed when tiny water droplets merge around particles of matter and become heavy and fall down to the earth.


Turning of water vapour into tiny water droplets as cooling continues below dew point. The droplets join to form clouds.

Causes of Condensation

  1. Adiabatic cooling-cooling of moist air as it rises vertically.
  2. Orographic cooling-cooling of moist air as it climbs a hill or mountain.
  3. Frontal cooling-cooling of warm air mass when it blows towards a cold air mass.
  4. Advection cooling-cooling as a result of moist air moving over a cool land or sea.
See also  RAINFALL

How Condensation Takes Place/Cloud Formation

  • Moist air rises to the condensation level (altitude where temperature is below dew point.
  • It’s cooled below dew point.
  • Tiny water droplets condense around tiny particles such as dust, smoke particles and pollen grains and salt particles (condensation nuclei).
  • The droplets merge and eventually become bigger and fall as rain.
  • If moisture rises to an altitude where temperature is below 0◦c the condensed water droplets freeze forming ice particles or super cooled water (water which has remained in a liquid state at temperatures below freezing point due to lack of sufficient condensation nuclei.
  • Super cooled cloud droplets may mould themselves around ice crystals before freezing to form hail.

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