Water Flashcards
Explain orographic rainfall
In upland areas Warm moist air rises Cools and condenses Forming rain Forms leeward rain shadow
What is a leeward rain shadow
Air descends
Pressure increases
Air contracts and warms
So it is drier on the other side of the mountain
Explain frontal rain
Where 2 fronts meet (a cold and warm) Warm air rises over cold air Undercut by colder air Fronts never mix and stay separated Warm air cools and condenses as it rises Forms cumulus clouds
Explain conventional rain
The surface ground locally is heated
Air above it is heated by conduction
It rises and cools and condenses
Forming cumulonimbus clouds (heavy rain)
Where does convectional rain happen
Tropics because it’s the warmest
Or in the summer
Explain collision theory
In tropics
Large amounts of warm moist air rises rapidly
Due to ground heat conduction
The raindrops falling from the top of cloud collide with water particles lower down
Leads to the coalescence of water particles
Droplets get bigger and heavier
So fall as rain
What is Bergeron findeisen theory
In the cold areas and high altitudes
Water vapour turns into ice crystals by sublimation due to super cooling
Ice crystals get heavier due to growth of more grazing nuclei
Ice crystals fall
but water vapour stays suspended due to air currents (because h2o is so small)
When it reaches the lower atmosphere the temperature increases so the ice melts due to friction with warmer air
How does urbanisation affect the water cycle
Replaces permeable surfaces (grass) with impermeable surfaces (concrete)
Increasing overland flow and surface run off
Reduces infiltration and through flow to soil storage
Decreased interception from trees
Means the rate of precipitation>infiltration
So increased surface run off
Less through flow
Increases flood risk
How much better is infiltration under trees than bare agricultural land
67x better
What is an aquifer
An underground layer of water bearing Permeable Rock of which groundwater can be extracted
Eg. Chalk
Why does the Uk become a carbon and water source in the winter
Deciduous trees lose leaves
Before frontal rain
Rain erodes bare soil due to lack of interception
Litter and soil transported into rivers
Explain the negative feedback cycle in the water cycle
Increased precipitation More overland flow Leaches minerals from soil Fewer plants Deforestation Decreasing precipitation
Exaplain the drainage basin system
Evaporation/ transpiration/precipitation Interception Stem flow Surface storage Surface run off Infiltration Soil moisture/through flow/channel storage/channel flow Percolation Ground water storage Veg storage
