SIGNIFICANCE OF HUMIDITY/MOISTURE \tAffects rain formation in such as way that places with high humidity are likely to experience higher rainfall than those with low humidity. \tRegulates the heat loss from the earth’s surface by absorbing terrestrial radiation (process in which the earth gives off heat into the atmosphere). \tIt affects sensible temperature in that the higher the humidity the more we experience sensible temperature. Precipitation -The forms in which the earth’s surface receives moisture. \t Snow Solid precipitation formed when tiny water droplets freeze and form ice crystals. The crystals may fuse to form flakes. \t Sleet -Precipitation which is a mixture of rain and snow. \t 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. \t Dew -Precipitation consisting of water droplets formed on cold surfaces at night e.g. iron roofs and glass blades. How It’s Formed \tIn a clear night there is a high ground radiation. \tTemperature of the earth’s surface fall below dew point (temperature at which air being cooled becomes saturated). \tExcess water condenses on cold surfaces. \t 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. Condensation Turning of water vapour into tiny water droplets as cooling continues below dew point. The droplets join to form clouds. Causes of Condensation \tAdiabatic cooling-cooling of moist air as it rises vertically. \tOrographic cooling-cooling of moist air as it climbs a hill or mountain. \tFrontal cooling-cooling of warm air mass when it blows towards a cold air mass. \tAdvection cooling-cooling as a result of moist air moving over a cool land or sea. How Condensation Takes Place/Cloud Formation \tMoist air rises to the condensation level (altitude where temperature is below dew point. \tIt’s cooled below dew point. \tTiny water droplets condense around tiny particles such as dust, smoke particles and pollen grains and salt particles (condensation nuclei). \tThe droplets merge and eventually become bigger and fall as rain. \tIf 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. \tSuper cooled cloud droplets may mould themselves around ice crystals before freezing to form hail.