Lecture 3 Flashcards
How are deep currents mapped
- they are mapped using subsurface floats
- >floats can float to a particular water depth or density to follow a mass
Describe the characteristics of subsurface floats
- can be set to float at a given depth
- > can also be specified to float within a given density surface to follow a water mass
- > returns to surface at intervals to send information
Describe the Argo program
- an international collaboration
- > since the year 2000
- > collects temperature and salinity profiles from the upper 2000 m of the ice-free global ocean
-also collects currents from intermediate depths using profiling boats
How does the Earth interact with short-wave radiation and long-wave energy
-earth is heated by visible short-wave radiation from the Sun and cools by radiating infrared(long-wave) energy back to space
What are the three things that Earth’s temperature depends on
- depends on the amount of incident sunlight, the planet’s reflectivity, and the greenhouse effect on the atmosphere
- note the radiation from the sun is absorbed on the planet by materials on the earth’s surface like rock and water
What is the proportion of the wavelengths of energy received from the Sun to the Earth
- 50% of energy is in the visible range
- 40% is the infrared radiation
- 10% is in the UV radiation range
What is the solar constant
- average energy flux from the sun at the mean distance of Earth
- > the amount of energy that a planetary body would be receiving from the Sun
- the Earth receives about 1366-1368 W/m from the Sun
- > as the Earth’s orbit is elliptical, not circular, this energy varies by 3.5% seasonally
What is solar incidence
- it is the total amount of solar energy that can be absorbed by the Earth
- > Solar Constant(S) x cross-sectional area(“flat” area of the Earth)
What is the total power of sunlight hitting the Earth
- that is the solar constant multiplied by the area of a circle
- > this power is distributed over the Earth’s entire surface
- > around 344 W m^2
Is the amount of solar energy that hits the Earth from the Sun 344 W x m^2
- no
- > because not all this energy is absorbed
- > a fraction(albedo) is relfected or scattered
- > an average albedo for the globe is 0.30
- > thus, actual solar energy received is 238 W x m^2
What does albedo mean
- the fraction of the sun’s radiation that is reflected from the surface
- > about 0.3 or 30%
Is albedo greater at higher altitudes or lower altitiudes
- it is higher at altitiudes
- > because there are more reflective surface like snow and ice
-lower latitude like equator have low albedo because of less reflective surfaces
What is the Earth’s energy budget controlled by in terms of incoming radiation and outgoing radiation
Incoming(solar irradiance)
- > temperature of the sun
- > distance from the sun
Outgoing Radiation
- > Earth’s reflectivity(albedo, A)
- > Radiated energy(blackbody radiation)
Describe the term Blackbody radiation
- a blackbody emits and absorbs radiation with 100% efficiency at all wavelengths
- > most objects behave similarly to blackbodies
How would you describe through a formula the energy received and reflected by the Earth
Energy received
->piR^2 x S
Energy reflected
->piR^2 x S x A(albedo)
-difference between energy received and energy reflected is the energy absorbed
What is the main greenhouse gas in the atmosphere
- it is water vapor
- >but there are other greenhouse gasses like carbon dioxide and methane which gets more attention
What is the net heat flux made up of
-it is made up of short waves(incoming solar radiation), long waves(infrared radiation reflected back), sensible heat and latent heat
Describe sensible heat
- flux of heat due to conduction
- > heat gained or lost by a body resulting in a change in temperature with no phase change
- direct physical contact between the atmosphere and the oceans leads to energy change by conduction
- > energy is transferred to the cooler molecules by molecular collisions
-note sensible heat is something that we can measure, touch or feel
What are the two factors that sensible heat flux depends on
-it depends on the local air-sea temperature difference and wind-speed
What is latent heat
- the hidden heat
- > not sensible, something we are measuring
- when water is evaporated, energy is supplied to the molecules to free them from the strong bonds in the liquid water
- when water molecules condense to form droplets, energy is released in the form of heat
- latent heat is very specific to phase changes
Does water have a very high heat capacity
-yes
Is heat exchange latent in polar regions? What does this mean?
- yes
- >this means that the ocean temperature changes very little over the course of the year
Why is the high latent heat of vaporization importaant for atmospheric heat transport
- head is added in the tropics
- > this warms the water and leads to evaporation
- > this heat is stored in water vapor molecules, which are blown to higher latitudes, where they condense as rain
- > the heat in these water molecules is released to the atmosphere, warming the higher latitudes
Is the incoming solar radiation evenly divided over the Earth
- no
- > there is a net surplus of radiation in the tropics and deficit at the higher latitudes
- > this leads to a transport of heat by the oceans and atmosphere from the equatorial regions to the poles
How does angle of impact of solar radiation play a role in the latitudes
- sunlight strikes at a high angle for the low latitudes
- > therefore, radiation is concentrated in a small area
-sunlight strikes high latitudes at a low angle so same amount of radiation is spread over a larger area
How does the atmospheric path length affect the amount of sunlight received at the latitudes
- Earth’s atmosphere absorbs some radiation
- > less radiation strikes Earth at high latitudes than low latitudes
- > because sunlight passes through more atmosphere at high latitudes
How does the differing albedo at different latitudes determine the amount of sunlight received
High albedo at the higher latitudes due to reflective surfaces(ice)
->therefore, the surface reflects the majority of radiation that hits it
Low albedo at the lower latitudes due to less reflective surfaces
->therefore, the surface absorbs majority of the radiation that hits it
What influences seawater temperature and salinity
- solar radiation
- transfer of heat and water with the atmosphere
- ocean currents
- vertical mixing
- runoff
