Precipitation

PRECIPITATIONIS release of water from atmosphere to reach surface of earth e.g. rainfall, snow, hail, sleetREQUIRES cooling of atmosphere usually by uplift of air through atmosphere (caused by heating from earth's surface, an air mass being forced to rise over an obstruction - mountain - or low pressure weather system where air is constantly being forced upwards., nuclei for water vapour to condense on e.g. small dust particles, sea salts, smoke particles growth of the water/ice droplets (condensation-formed, collision-formed or Bergeron-process-formed) Dewfall is another form of precipitation but is not normally a major part of hydrological cycleAMOUNT OF PRECIPITATION influenced by Static and Dynamic influencesStatic influences (of decreasing impact) Altitude - due to effect on temperature Aspect - those facing away from predominant weather patterns will receive less rainfall than those facing them. Slope - normally ignored RAIN SHADOW EFFECT (static) where a large and high land mass blocks the rain, causing it to fall on one side while preventing it from moving to the other (e.g. southern alps)Dynamic (changing) mainly caused by weather variationsForest Rainfall Partitioning - once rain reaches tree canopy various things can happen Throughfall - rain falls to ground directly or indirectly via leaves branches. Amount that reaches ground determined by canopy (cover one measure of which is Leaf Area Index - surface area of all leaves in canopy to surface area of ground), canopy storage capacity and rainfall characteristics (intensity, angle etc.) Stemfall Interception loss Interception gain