ELSS- importance of water and carbon for life

earths life support systems first specification point

Uses of water for flora, fauna, people and climate

• crucial for cell function in all living things

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Flora

• photosynthesis, respiration and transpiration

• transportation of minerals/nutrients

• rigidity

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Fauna

• sweating

  • similar to transpiration

• evaporative cooling- panting

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People

• sweating

• medium for all chemical reactions

  • circulation of oxygen

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Carbon

• economic resource

• life built on C atoms

• stored in atmosphere, biosphere, carbonnate rocks

Cryosphere

the frozen part of the Earths surface, including the polar ice caps, continental ice sheets, glaciers, sea ice and permafrost

Hydrosphere

all the waters on the Earths surface such as seas

• as a globe, water cycle is a closed system

• at local scales it is an open system

Atmosphere

the envelope of gases surrounding the planet

Biosphere

the space within the Earths surface and the atmosphere occupied by living organisms

Lithosphere

the rigid outer part of the Earth, consisting of the crust and upper mantle, divided into tectonic plates

Throughflow

water will always move downwards due to gravity but water may be deflected by soil particles and impermeable soil components

Overland flow/surface runoff

may be caused by naturally impermeable surfaces i.e. tarmac or those which have become so as a result of compaction

Interception

• when precipitation lands on vegetation

• the volume of water intercepted is dependent on the nature of the vegetation

Leafdrip

the total volume of water which drips from leaves is influenced by the shape of the leaf, the presence or absence of any waxy cuticle and the surface form of the leaf

Stemflow

• the flow of intercepted water down the trunk or stem of a plant

• greatest on trees which have smooth bark and steeply-angled branches

Throughfall

refers to intercepted water dripping off leaves and branches to the ground

Direct impact

• raindrops possess considerable kinetic energy

• total amount of energy transmitted to the soil surface is proportional to the product of rainfall intensity and duration

• accumulating leaf litter dissipated the energy

Transpiration

• loss of water through stomata in leaves

• combination of evaporation and transpiration is known as evapotranspiration

Infiltration

• absorption of water into the soil

• rate influenced by soil porosity

  • determined by the nature and arrangement of the soil peds

• decomposed leaf litter adds organic matter to the soil

  • improves its structure, hence permeability, encouraging more efficient infiltration

Surface storage

the total volume of water held on the Earths surface in lakes, ponds and puddles

Soil water storage

the amount of water stored in the soil

Groundwater storage

water stored underground in permeable and porous rocks known as aquifers

Channel storage

the water held in a river or stream channel

Groundwater flow

the horizontal movement of water within aquifers

• very slow

Sublimation

change of state from solid to gas —> dry ice

Deposition

change of state from gas to ice

Potential evapotranspiration (PET)

• the amount of water that could evaporate if there was limitless supply

• e.g a desert should have the highest PET, but it doesn’t

  • because there is no water and very little vegetation

Condensation

the process of water vapour converting to a liquid

Troposphere

• lowest portion of the atmosphere

• where all weather takes place

• contains approx 75% of the atmosphere’s mass and 99% of its water vapour and aerosols

Temperature of air as you travel up through the troposphere

• gets colder

• approx 6.5°C per km

• varies depending on height, season and over surfaces i.e. ocean vs land

Environmental lapse rate (ELR)

the decrease in temperature usually expected with an increase in height through the troposphere

What is a lapse rate

describes the vertical distribution of temperature in Earth’s atmosphere, and the temperature changes that occur in an air parcel as it rises vertically

Why does it not get hotter closer to the sun

• the troposphere is primarily heated from the bottom because the surface is much better at absorbing a wide range of solar radiation as compared to the air

• the surface is warmed by the sun and then this energy warms the air above the ground through conduction

• this warm air rises upwards into the troposphre through convection

Air pressure

• refers to the weight of the Earths atmosphere pressing down on everything

• average air pressure at sea level is 1.03kg per square centimetre (kg/cm²)

• measured in bars

• atmospheric pressure = roughly 1 bar

• air pressure decreases as you move up through the atmosphere

Adiabatic expansion

• description of what happens to a parcel of air as it rises as air pressure decreases

• causes an increase in volume and a decrease in temperature

Rate of cooling of a parcel of air

depends on how saturated the air is

Dry Adiabatic Lapse Rate (DALR)

• the rate at which a parcel of dry air (less than 100% humidity, condensation not taking place) cools

• cooling is approx 10°C/km

Saturated Adiabatic Lapse Rate (SALR)

• the rate at which a saturated parcel of air (one in which condensation is occurring) cools as it rises through the atmosphere

• rate is cooling is slower than DALR

  • approx 7°C/km

  • because condensation releases latent heat

Cloud formation

• form when rising air has cooled to the dew point

• once condensation begins latent heat is produced

  • air continues to rise but cools more slowly (SALR)

• when the parcel of air reaches a temperature the same as that surrounding it, it will stop rising

  • air is now stable

Topographic/orographic uplift

• the topography can cause clouds to form

• air is forced to rise over a barrier of mountains or hills and it cools as it rises

• layered cloudsnare often produced this way

  • i.e stratus clouds and lenticular clouds

Convergence of air masses

• streams of air flowing from different directions are forced to rise where they flow together/converge

• can cause cumulus clouds and showery conditions

Cumuliform clouds

• large and puffy

• can stretch vertically into the atmosphere up to 12,000 metres high

• created by strong updrafts of warm, moist air

• most heavy rainfall comes from cumulus clouds

• usually found in fair weather

Stratiform clouds

• horizontal and layered

• blanket the entire sky in a single pattern

• usually occur close to the Earth

• fairly uniform grey or white colour

Advection: transfer of heat through the horizontal movement of air

• form at the boundary of a warm front, where warm, moist air is forced up over cold air

• produces clouds as the moist air is cooled across the entire front

• can exist in a variety of thicknesses

Cirrus clouds

• short, wispy, detached clouds

• found at high altitudes

• form from the ascent of dry air, making the small quantity of water vapour in the air undergo deposition into ice

• made completely from ice crystals

• signal clear, fair weather

• shape indicates the direction the wind is blowing