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precipitation - cold air holds less water vapour than warm air - Coggle…
precipitation - cold air holds less water vapour than warm air
intensity of precipitation
amount of precipitation falling in a given time
high-intensity precipitation moves rapidly overland into streams and rivers. flashfloods
this in turn effects the type of overland flow
saturated overland flow
: ground is saturated/waterlogged, no more can be absorbed, normally water table rises up to the surface.
infiltration excess overland flow
: rate of precipitation is greater than the rate it can infiltrate the soil. summer, ground is dry/baked over a long period of time, hard crust on surface, few pour spaces, takes longer for rain to wet it, flows over the surface
type of precipitation (rain or snow)
rain: most rain upon reaching the ground flows quickly into streams + rivers.
either overland or infiltration excess, depending in intensity of rain (infiltration excess) or long duration (saturated overland flow)
snow: in high latitudes + mountainous catchments, precipitation falls as snow
remains on ground for several months
creating a significant time lag between snowfall and run off
can't flow until solid, overland flow insignificant, only until snow melts
seasonal variation
diurnal (day + night)
less evaporation at night
not a big issue in the uk
tropics, day: ground gets heated, convection currents forming + big storm clouds develop. afternoon: rainfall
pattern in arctic, precipitation too cold to occur and night
saturated overland flow
: winter and spring higher levels of precipitation, soil moisture store lower in the summer
infiltration excess overland flow:
occur any time of year, but summer in the uk, heavy thunderstorms in summer (stronger convection currents and temperature)
duration of precipitation
the length of time that a precipitation event lasts
prolonged events, linked to depression + frontal systems may deposit exceptional amounts of precipitation and cause river flooding
saturated overland flow
, more likely to occur