Earth's Life Support Systems Flashcards
Inputs of the water cycle to the atmosphere
To the atmosphere - water vapour evaporated from the oceans, soils, lakes and rivers, and vapour transpired through the leaves of plants - together known as evapotranspiration
Outputs of water to the atmosphere
Moisture leaves the atmosphere as precipitation ( rain, snow, hail) and condensation (fog)
Ice sheets, glaciers and snowfields release water by ablation (melting and sublimation)
Inputs and outputs of water - precipitation
Precipitation and meltwater drain from the land surface as runoff into rivers. Most rivers flow to the oceans through some drain to inland basins. A large part of water falling as precipitation on the land reaches rivers only after infiltrating and flowing through the soil.
Inputs and outputs of water cycle - rocks
After infiltrating the soil, water under gravity may percolate into permeable rocks or aquifers. This groundwater eventually reaches the surface as springs or seepages and contributes to runoff
The slow carbon cycle formation
Co2 diffuses from the atmosphere into the oceans where marine organisms, such as clams and corals, make their shells and skeletons by fixing calcium to form calcium carbonate.
On death the remains of these organisms sink to the ocean floor. There they accumulate and over millions of years, heat and pressure convert them to carbon rich sedimentary rocks
Fast carbon cycle process - organisms
Land plants and microscopic phytoplankton - through photosynthesis they absorb co2 from the atmosphere and combine it with water to make carbohydrate.
Respiration by plants and animals is the opposite process and results in the release of co2. Decomposition of dead organic material by microbial activity also returns co2 to the atmosphere
Fast carbon cycle process - oceans
Atmospheric co2 dissolves in ocean surface waters while the oceans ventilate co2 back to the atmosphere. Through this exchange individual carbon atoms are stored by natural sequestration in the oceans for about 350 years
What are the flows of the water cycle
Precipitation
Transpiration
Condensation
Cloud formation
How does precipitation form
Vapour in the atmosphere cools to its dew point and condensed into tiny water droplets or ice particles to form clouds. Eventually these droplets or or ice particles aggregate, reach a critical size and leave the clouds as precipitation
How can precipitation vary
Most rain flows quickly into streams and rivers - in high latitudes and mountainous areas precipitation may fall as snow and may remain on the ground for several months
Different intensity change speed of runoff
Different duration
Rain seasons
What is transpiration
The diffusion of water vapour to the atmosphere from the leaf pores of plants. It is responsible for around 10% of moisture in the atmosphere
What is condensation
The phase change of vapour to liquid water. It occurs when air is cooled to its dew point. At this critical temperature air becomes saturated with vapour resulting in condensation.
What are cumuliform clouds
Flat bases and consideration vertical development most often form the earths surface. These causes heated air parcels to rise freely through the atmosphere, expand and cool. As cooling reaches the dew point, condensation begins and clouds form
Stratiform clouds
Develop where an air mass moves horizontally across a cooler surface (often the ocean). This process is known as advection
Cirrus clouds
Form at high altitudes and consist of tiny ice crystals. Unlike cumuliform and stratiform clouds they do not produce precipitation and therefore. Have little influence on the water cycle
How do cooling to form clouds occur
Air warmed by contact with the ground or sea surface, rises freely through the atmosphere. As the air rises and pressure falls it cools by expansion. This vertical movement of air is known as convection
Air masses move horizontally across a relatively cooler surface (advection)
Air masses rise as they cross a mountain barrier or as turbulence forces their ascent
A relatively warm air mass meets a cooler one
What is a lapse rate
Describe the vertical distribution of temperature in the lower atmosphere, and the temperature changes that occur within an air parcel as it rises vertically away from the ground.
What is environmental lapse rate
ELR is the vertical temperature profile of the lower atmosphere at any given time
On average the temperature falls by 6.5 degrees for every kilometre of height gained
What is the dry adiabatic lapse rate (DALR)
The rate at which a parcel of dry air cools. Cooling is approximately 10 degrees/km
What is saturated adiabatic lapse rate (SALR)
The rate at which a saturated parcel of air cools as it rises through the atmosphere. Because condensation releases latent heat, SALR is around 7 degrees/km
What is evaporation
Phase change of liquid water to vapour and is the main pathway by which water enters the atmosphere
What is interception
Vegetation intercepts a proportion of precipitation, storing it temporarily on branches, leaves and stems. Eventually the moisture either evaporates (interception loss) or falls to the ground
What is throughflow
Rain water that is briefly intercepted before dripping to the ground
What is stem flow
Intercepted rainfall may flow to the ground along branches and stems
How can rainfall reach streams and rivers
Infiltration by gravity into the soil and lateral movement or throughflow to streams and rivers
Overland flow across the ground surface either as a sheet or as trickled and rivulets to river and stream channels
Factors affecting interception loss
Interception storage capacity
Wind speed
Vegetation type
Tree species
What is interception storage capacity
Before the onset of rainfall, vegetation surfaces are dry and their ability to retain water is at a maximum. Initially most rainfall is intercepted. However, as vegetation becomes saturated, output of water through stemflow and through fall increases. Interception therefore depends on the duration and intensity of a rainfall event
How does wind speed affect interception loss
Rates of evaporation increase with wind speed. Turbulence also increases with wind speed causing additional through fall
