Energy balance
Sun
Energy balances in the
Atmosphere-Ocean system.
Energy balance
Uneven solar heating on Earth:
In space:
In time (seasons):
Solar energy in high latitudes:
‒ Earth’s axis is tilted from vertical
– Spreads over a large area
‒ N and S Hemispheres are alternately
– Is reflected to a greater extent
tilted toward and away from the Sun
– Passes through more atmosphere ‒ More solar energy during summer
Energy balance
Balance of the solar radiation on a monthly basis
-100 -50 -25
0
25 50 100 125 150 200
Wm-2
Energy balance
Oceanic heat flow
Net energy
transport
Transport by
the ocean
Relative fraction
Transport by the
atmosphere
Oceans – northern
hemisphere
Oceans
southern
hemisphere
The excess of energy in the low
latitudes has to be transported
to the high latitudes
North or South
Heat transport by the
Ocean and Atmosphere
Energy balance
The transport of heat by the ocean determines the
large ocean circulation…..
Here, only the surface transport is represented…..
….the well known
energy Conveyor Belt:
Contribution of each Ocean:
Energy balance
Energy balance
If the energy balance is destroyed….?
greenhouse effect
Energy balance
Energy balance of the Earth (and Oceans….):
Incoming energy = outgoing energy
Outgoing energy
Incoming energy
Terrestrial spectrum at 3 sites
Solar radiation spectrum
Energy balance
Carbon dioxide is increasing in the atmosphere
As a result of human
activities, carbon dioxide
in the atmosphere has
increased by 30% since
200 years ago
Earth’s average temperature is rising
Earth’s average surface
temperature has risen at least
0.6°C in the last 130 years
Is this related to increase in
atmospheric carbon dioxide?
Energy balance
Heat balance of the Oceans
Remember:
__ __ __ __
Qs = Qb + Qe + Qh
Qs – Electromagnetic radiation of short-wavelength with solar origin (~ 340 W/m2
in the top of the atmosphere; ~ 225 W/m2 at the sea level)
Qb - Electromagnetic radiation of long-wavelength emitted by the ocean surface
and by the atmospheric boundary layer just above the ocean surface (8 to 14µm).
Qe – Latent heat lost by evaporation or gained by the condensation of the water
vapour on the sea surface (~ 100 W/m2)
Qh – Sensible heat exchanged by conduction between the ocean and the
atmosphere when they are at different temperatures (~ 15 W/m2, very variable)
Magnitude of the fluxes
Energy balance
Annual average heat fluxes (W/m2). (a) Short-wave heat flux Qs. (b) Long-wave (back adiation)
heat flux Qb. (c) Latent (evaporative) heat flux Qe. (d) Sensible (conduction) heat flux Qh.
Positive (yellows and reds): heat gain by the sea. Negative (blues): heat loss by the sea.
Contour intervals are 50 W/m2 in (a) and(c), 25 W/m2 in (b), and 15 W/m2 in (d).
Energy balance
Net heat flux
Annual average net heat flux (W/m2). Positive (yellows): heat gain by the sea. Negative
(blues): heat loss by the sea. Compare with the radiation balance for the entire Planet,
presented in slide 8
Distribution of the fluxes along the latitudes
Heat input through the sea surface (where 1 petawatts,
PW = 1015 W) (world ocean) for 1º latitude bands for all
components of heat flux.
Energy balance
Energy balance
Consequence:
Sea Surface Temperature (SST) of the World Ocean
 SST changes along the year due to the seasonal variations of the
solar radiation.
• In the equatorial latitudes, changes are minimal.
• At high latitudes, the small changes are due to the permanent
presence of ice.
• The largest seasonal differences occur in the middle latitudes.
February
August
Energy balance
A note about understanding the satellite SST:
Connect https://www.ghrsst.org/ for details
Mass balance
Mass interaction - Mass balance
(dictated by the hydrological cycle)
Main factors: evaporation vs. precipitation; terrestrial run-off
Average salinity distribution along the latitude:
Mass balance
• High latitudes have low
surface salinity
– High precipitation and
runoff
– Low evaporation
• Tropics have high surface
salinity
– High evaporation
– Low precipitation
• Equator has a dip in surface
salinity
– High precipitation partially
offsets high evaporation
Mass balance
Global surface
salinity
Net evaporation and
precipitation (E–P) (cm/yr)
based on climatological
annual mean data(1979–
2005) from the National
Center for Environmental
Prediction. Net precipitation
is negative(blue), net
evaporation is positive (red)
Mass and energy balance
Joint effect of energy and mass balance:
density distribution
Mass and energy balance
In the end, all the motion in the ocean is driven trough the atmosphere...
The ocean is permanently moving, with scales from the large currents to the
small eddies. The very beginning of all those motions is the solar radiation! • The Sun influences the ocean circulation through the atmospheric circulation.
The energy is transfered from the wind to the upper layers of the ocean
through the frition between the atmosphere and the sea surface  wind
driven circulation (to see later….)
• The Sun causes variations in the temperature and salinity of the sea water.
These control the density. Variations in the temperature are caused by heat
fluxes through the air-water interface. Variations in the salinity are caused by
the addition or subtraction of fresh water through precipitation, evaporation, or
ice-water melting in the polar regions. When the surface water becomes
denser than the underlying water, it becomes unstable and it sinks.This
circulation is driven by the density  thermohaline circulation