Precipitation Flashcards
Where does precipitation come from?
Water vapor generated by solar radiation from land and ocean. Product of condensation of atmospheric water.
What is relationship between air pressure, moisture and likelihood of rain?
Low air pressure = high moisture = high chance of rain
Why is specific heat for water vaporisation used to find the energy released from storms?
Vaporising water requires same amount of energy that is released when water is condensed.
What equation is used to calculate energy and power release from storms?
Energy = Mass of water x specific latent heat
Power = E / time of event
What conditions are required for precipitation?
Sufficient water vapor
Low Temperature (from high elevations)
Cloud condensation nuclei or CCNs (cloud seeds)
Explain how you can change weather conditions chemically
Add impurities in clouds such as seeding them with salt to prevent floods and cause conflict between countries.
What 2 processes can produce precipitation?
Ice crystal process
Coalescence process
Explain the ice crystal process
Occurs during cold season. Aerosols act as freezing nuclei. Ice crystals grow in size and fall to ground.
Explain the coalescence process
Occurs during the warm season. Vapor condenses to liquid directly. Small droplets collide until become too heavy and fall.
What are the 3 main categories of how precipitation is vertically transported?
Convective
Orographic
Cyclonic
Explain convective precipitation
Heated air near the ground expands and absorbs more water moisture. The warm moisture-laden air moves up and gets condensed due to lower temperatures thus producing precipitation. Occurs during summer.
Explain orographic precipitation
Uplifting of air is caused by natural barriers such as mountain ranges. i.e when air moves across land it gets pushed up due to a mountain
Explain cyclonic precipitation
Uneven heating of Earth causes high and low pressure regions and air masses move from high to low pressures. If warm air moves above cold air or pushed up by cold air it causes precipitation.
How can rainfall distribution be explained for the UK?
Orographic precipitation since westerly winds push clouds up mountains to cause rainfall along western coast.
Explain a warm front
Warm air replaces colder air and clouds develop because warm moist air is lifted.
Explain a cold front
Cold air displaces warm air and clouds develop because warm moist air is lifted.
What effects does a rain drop experience?
Gravitational, buoyancy, and air resistance.
What are properties of a large rain drop?
Falls faster and collects more water during fall however if it is too large it breaks into smaller droplets.
How are precipitation events recorded?
Rain gauges - collect point precipitation data
Radars - observe fall from sky
What is force balance on a rain drop?
Drag force = gravity force - buoyancy
What is used to check the data quality of a specific rain gauge?
Double Mass Curve
Explain the how to construct a double mass curve and interpret the data.
Plot a scatter plot between interested gauge and a number of surrounding gauges cumulatively.
Change determined if trendline gradient changes.
Find the correction ratio by Average Gauge X / Average Other Gauges both before and after point of change then ratio = before/after
Ratio is used to create consistent linear relationship where Gauge X average x correction ratio = accurate estimation.
What are double mass curve’s aims?
- Examine consistency of Gauge X
- Find when a change in regime occurred
- Discuss possible causes
- Adjust the data
Why would data for a rain gauge change?
Re-sitting, blockages like growing trees etc.
