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Flashcards in fluid environment and behaviour Deck (51)
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1
Q

what was the earths atmosphere when it was first formed?

A

it was initially surrounded by gas molecules gravitationally attracted to its surface from the gas molecules and dust rings surrounding the newly born sun.

2
Q

what did the primary atmosphere consist of?

A

This primary atmosphere consisted mostly of hydrogen, helium and traces of other gases.

3
Q

what happened to the atmosphere due to the heat?

A

Heat from the sun caused light atoms in it to move around so rapidly, that they eventually escaped the attraction of the earth’s gravity. The primary atmosphere leaked out into space, blown away from the solar winds.

4
Q

what did the secondary atmosphere consist of?

A

volcanic activity caused this, as it releases a new set of gases. The elements in these gases had been bonded to minerals inside the earth. Water vapor, CO2, SO2, N2, and NH3. the secondary atmosphere consisted of these gases, plus some gases brought to earth by some comets.

5
Q

what happened when the earth cooled sufficiently?

A

When the earth cooled sufficiently for water to condense, around 3.8 Ga, rain extracted most of the water from the atmosphere.

6
Q

when the earth cooled and the water condensed, what happened to the earth?

A

this water made the lakes, filled the oceans, streams, or sank underground to become groundwater. The concentration of CO2 in the atmosphere began to decrease when this occurred. This is due to the CO2 dissolved in oceans and them combines with calcium to form solid carbonate. Co2 also reacts with rocks exposed on the surface of continents to produce solid chemical weathering products.

7
Q

what did UV radiation cause in the secondary atmosphere?

A

UV radiation from the sun split apart molecules of NH3 into nitrogen and hydrogen atoms. The H escaped to space, but the N formed N2, and due to it being unreactive with rocks, it has stayed in the atmosphere for a long time. Due to the new accumulation of N2 molecules, and the loss of water vapour and CO2, the proportion of N gradually increased.

8
Q

when did photosynthetic organisms appear?

A

3.8 Ga

9
Q

what happened to the oxygen when life started?

A

It took the appearance of life on earth to introduce oxygen to the atmosphere, as O2 is produced due to photosynthesis. The first photosynthetic organisms, cyanobacteria, appeared on earth at around 3.8 Ga, and began to add oxygen to the atmosphere.

10
Q

what does dry air consist of?

A

Dry air consists of 78% nitrogen, 21% oxygen. Remaining 1 % consists of other gases such as CO2, CH4 which are greenhouse gases that regulate the earths atmosphere.

11
Q

what do greenhouse gases allow?

A

Greenhouse gases allow solar radiation from the sun t o pass through, but trap infrared radiation rising form the earths surface. Trace gases also contain O3, ozone, which protects the surface from UV radiation. In addition to these gases, the air contains traces of aerosols. These tiny particles of liquid or solid material, are so small that they remain suspended in river water.

12
Q

what are aerosols?

A

Aerosols include tiny droplets of water and acid and microscopic particles of sea salt, volcanic ash, clay, soot and pollen.

13
Q

how has human activity increased pollutants? (3 areas)

A

Human activity has added a substantial amount of pollutants to the air, due to fossil fuel burning and industrial operations. Pollutants include sulfate and nitrate molecules, which react with water to make a weak acid that falls as acid rain. Where acid rain falls, lakes and rivers become acidic and toxic to fish and life in the water sources. The burning of fossil fuels has increased the amount of CO2 in the atmosphere, this contributes to global warming. Atmospheric scientists have discovered that some pollutants react with UV light from the sun to release Cl atoms which react with the ozone, and break it down. These reactions appear to happen mainly in high clouds above polar regions during certain times of the year.

14
Q

how do elevations determine the weight of air?

A

In the earths gravity field, the weight of air at higher elevations presses down on and compresses air at lower elevations.

15
Q

what is air pressure and what does it do?

A

Air pressure- the push the air can exert on its surroundings. And air density, therefore increases towards the surface of the earth. Beacuse of the density of a gas reflects the number of gas molecules in a given volume, a gulp of air on top of mount Everest where the air pressure is about one third taht of sea level, contains about a third of O2 molecules than that of sea level.

16
Q

what is 1 atm?

A

1 atm is approx the pressure exterted by the atmosphere at sea level.

17
Q

how many molecules lie below an elevation of 5.6 km and why?

A

Because of the decrease in air density with elevation, 50 % of the amtopsheres molecules lie below an elevation of 5.6 km.

18
Q

where is the boundary of gas density?

A

Even though the outer edge of the atmosphere, a vague boundary where the gas density becomes the same as interplanetary space, lies as far as 10,000 km away from the earths surface, most of the atmospheres molecules lie within a shell only of 0.5% as wide as the solid earth.

19
Q

what are the molecules doing in the atmosphere?

A

The molecules that constitute the atmosphere are not standing still but are constantly moving. The total kinetic energy. Resulting from the movement of molecules in a gas as its not the same- a gas’s temperature is a measure of the average kinetic energy of its molecules.

20
Q

how many molecules are in a volume of gas?

A

A volume of gas with a small number of rapidly moving molecules has a higher temperature, but may contain less heat than a volume with a large number of slowly moving molecules.

21
Q

what is dewpoint?

A

The temperature at which the air becomes saturated is called the dewpoint temperature. This is when water condenses on surfaces. When the dewpoint temperature is below freezing, frost develops. And when moist air rises and adiabatically cools, its moisture condensed to form a cloud- mist of tiny droplets.

22
Q

what is latent heat of condensation?

A

When water in the air changes from liquid to gas, or vice verca, (change of state), the temperature of the air can also change. That is, when the water evaporates, it absorbs heat, so that the molecules can break free from the liquid. The condensation of water reverses this process, and hence releases heat. The heat released during condensation is hidden, in the sense that is comes only from the change of state and doesn’t require an external so energy source. Thus is called latent heat of condensation.

23
Q

what are the properties and behaviours of fluids?

A
  • Controls on seawater composition and residence times
    • Salinity temperature, control on density of seawater, constituents of seawater, controls on density
    • Behaviour of layered and stratified fluids, the density and layering, convection, examples of interface as boundaries and barriers.
24
Q

what is the control on seawater composition?

A

Seawater is a solution of many different chemical compounds, the concentrations of dissolved substances determined by their global abundance and their behaviour in chemical and biogeochemical cycles. They have reached a balanced equilibrium.

25
Q

what is the balance between input and output?

A
  • Conc if a substance un seawater is determined by the rate at which it enters the ocean and the rate at which it is removed.
    • The oceans have participated in biogeochemical cycling for billions of years so that concentrations of dissolved substances have reached a steady state.
    • There is a balance between the input and output. Between sources and sinks
26
Q

what elements have the shortest residence times?

A

input and output. Between sources and sinks

• The conc of elements in seawater are determined largely by the effectiveness of processes taht remove them.

27
Q

what is salinity?

A

• Salinity- units are given in per mile (parts per thousand). Grammes of salt per1 kg of seawater, mainly NaCl. Units are PSU- practical salinity unit.

28
Q

what is the density of seawater? and when does it increase?

A

the density of water increases as the salinity increases. The density of water (salinity >24.7), increases as the temperature decreases at all temp above freezing point. The density of seawater is increases by increasing pressure, about 2% higher in the deep ocean than the surface water.

29
Q

what are the maximum of salinity?

A

• Water of salinity less than 24.7 has an anomalous density maximum. Pure water has its maximum of 4 degrees density. Sea water max density of seawater occurs at lower temperatures as salinity increases.

30
Q

why does seawater freezing decrease as purity of water decreases?

A

• Between4 degrees and the freezing point, the density of pure water decreases as the tempertaure decreases. This is due to the hydrogen bond. Because there is a salinity range, most seawater freezes at -2 degrees.

31
Q

how do we measure salinity?

A

We don’t evaporate and weigh the salts, we measure conductivity.
Hence- CTD probe - conductivity, temperature (thermometer), and depth (pressure gauge).

32
Q

what is a simple convection cell?

A

water is heated at the bottom of an pan, causing the water to rise. On reaching the surface, the warm water spreads out, cools and then sinks down to the side of the pan to be heated again.

33
Q

what are inversions?

A

Inversion layers act as interface or barrier. This forms where there is a reverse T gradient, and zone of inverse T gradient.
Examples of layering- tropopause- a major interface in the earths system due to reverse in T gradient. Now known to be more porous than previously thought.

34
Q

what are examples of inversions?

A

tropical tropopause, silhouettes of thunderstorms with cirrus anvil tops spreading out along the tropopause.

35
Q

why do different levels of desntiy separate in layers?

A
  • Density and layering in fluids. The less dense fluids reset above denser fluids. The boundary between the fluid of different densities form an interface. The air, and water interface is the most significant.
    • When there is an inversed density gradient, we get convection. Easiest way to get this is thrugh heating it.
36
Q

how are vertical motions in a fluid be causes?

A

• Vertical motions in a fluid can be caused by temperature or compositional changes that alter the density of parts of the fluid.

37
Q

what happens to density if the fluid is cooled?

A

If cooled of density increases by another process, eventually the fluid is dense enough to sink back to its original level where it replaces the rising fluid and renters the cycle.

38
Q

what are divergences?

A

• At the top of the convection cell, divergences are regions of upwelling. At the bottom of the convection cell, convergences are regions of upwelling.

39
Q

what are connection cells and where are they found?

A

• Connection cells are found in the mantle, oceans and atmosphere. At the earth and ocean surfaces mantle and ocean convection cell convergences are downwelling zone and divergences are upwelling zones.

40
Q

what is the earth radioactive balance?

A

The energy that drives the earths system heating- the earths radioactive balance orbital tilt/ obliquity and the seasons
The earths radioactive balance, radioactive imbalance and hear transport, heat drives atmospheric circulation, evaporation, precipitation. Earths orbit and seasonality, motion on a rotation earth- the Coriolis effect.

41
Q

how is the surface temperature of the earth determined?

A

• The surface temperature of the earth is determined mainly by its radioactive energy balance.

42
Q

how can a planet maintain a constant temperature?

A
  • An object emits electomagnetic radiation at a wavelength related to is temperature.
    • The suns peak emissions are in the visible light ban (shortwave). Earths emissions are in the infrared band of longwave.
    • In order for a planet to maintain a constant average temperature, the amount of energy it radiates must equal the amount of solar energy radiation it absorbs.
    • The amount of the sun’s radiation that a planet absorbs will depend on tis albedo or reflectance.
    • The surface without snow or ice, absorbs more heat. The surface of the snowball earth, reflects ore heat.
43
Q

how can you calcuate the earths temperature?

A

• We know incident radiation from the sun, we know the earths albedo, so assuming energy balance we can calculate earths temperature.

44
Q

how does T control the balance of heat?

A

If the surface is 228K, the earth will emit too much heat to maintain balance. IR absorb bases reduce T at which emissions to space occur. Lower effective emissions T of earth and maintain energy balance.

45
Q

what is stable stratification?

A

• Stable stratification- is when it is all separated. In the atmosphere it tends to get colder at the top- inverse stratification, as it has denser and colder air which lies above warmer less dense air, this is why it is so unstable and why we have weather.

46
Q

when does interface occur?

A

• Interface occur when there is a change of density, and where there is a change in temperature. They act as barriers of communication between fluids. Acts as barriers to exchange of properties such as nutrients in the ocean.

47
Q

what happens if the density continues to decrease in oly one fluid layer?

A

If the density continually decreases in one fluid layer and increases in a higher layer, a convection cell is established. In a convection cell, a plume of the lowered density fluid rises until it reaches an equilibrium level where surrounding fluid of equal density and spreads out.

48
Q

what are convergences and how are they altered with divergences?

A

• Convergences and divergences must be altered across both the upper and lower boundaries. At the top of the convection cell, divergences are regions of upwelling. Convergences are regions of downwelling. At the bottom of the convection cell, divergences are regions of downwelling. Convergences are regions of upwelling.

49
Q

what is incoming short waves?

A

Incoming short-wave (UV/visible) radiation, which is affected by reflection, due to water, soils, vegetation, clouds

50
Q

what is outgoing long waves?

A

Outgoing long wave (Thermal IR) radiation- which is affected by absorption and re-emission by certain atmospheric gases. Causing the greenhouse affect. Mostly natural, due to water vapour

51
Q

what is the planetary temperatures caculated from radioactive balance?

A

Planetary temperatures calculated from radioactive balance: mercury has no atmosphere so it is pretty close. Venus is way out, and mars also close as it has little atmosphere. Atmosphere has to be taken into account.
Take greenhouse gases into account, the greenhouse gases absorb outgoing LWR and radiate it in all directions including downwards