AL Energy Budget ` Recap zWhen solar radiation reaches the earth, the incoming solar radiation being...
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Transcript of AL Energy Budget ` Recap zWhen solar radiation reaches the earth, the incoming solar radiation being...
Recap
When solar radiation reaches the earth, the incoming solar radiation being reflected scattered absorbed
When it reaches the ground, some is being reflected (shortwave radiation).
The ground converts the insolation into longwave outgoing radiation.
The incoming solar radiation
Total 100
Scattered to space 5
Scattered to ground 6
Reflected by cloud 21
Reflected from ground 6
Absorbed by atmosphere 15
Absorbed by cloud 3
Absorbed by ground 50
The outgoing radiation
Total
Sensible heat transfer 9
Latent heat transfer 20
Ground radiation absorbed by atmosphere
90
Ground radiation to space 8
Radiation to the space 60
Counter-radiation to the ground 77
Energy Budget Table
Formulate three energy budget tables according to the three different components:
earth system atmospheric system earth-atmospheric system
Heat balance at the ground surface
Gain
The balance of gain
Loss
The balance of loss
Short-wave radiation from the sun 50Counter-radiation from the atmosphere 77 127
Long-wave radiation to the space 8Long-wave radiation to the atmosphere 90Latent heat flux to the atmosphere 20
Sensible heat flux to the atmosphere 9127
Heat balance at the atmosphere
Gain
The balance of gain
Loss
The balance of loss
Short-wave radiation from the sun 18
137
Long-wave radiation from the ground 90Latent heat flux from the ground 20
Counter-radiation to the ground 77
Sensible heat flux to the space 9
137Long-wave radiation to the space 60
Latitudinal distribution of solar radiation
The annual solar radiation received along the equator is very high but not the highest
Due to the presence of cloud cover ( ITCZ)Inter-tropical Convergence ZoneBetween 10o-20o N and S, there receive most
solar radiationThe angle of incidence is highLack of cloud cover
Latitudinal distribution of solar radiation
At high latitudes, there is less radiationBecause the angle of incidence is lowHigh albedo because of snow coverMore insolation in Northern HemisphereBecause there is more land surface and less
cloud cover
Difference between Figure 2.13 and 2.15
Fig. 2.13 shows annual solar radiation but Fig. 2.15 shows the net radiation
Annual solar radiation considers incoming solar radiation only
Net radiation is nthe difference between incoming solar radiation and outgoing solar radiation.
TWO characteristics in spatial variation
The net radiation amount of ocean is greater than land at the same latitude.
Net radiation decreases with increasing latitude.
Difference between S. Hemisphere and N. Hemisphere
The net radiation amount at equivalent latitudes in the S. Hemisphere is more than the N. Hemisphere
because there are more ocean, then there is more cloud cover.
Variation in Average Annual Net Radiation
At nearly all latitudes, net radiation of the earth surface is above zero.
Energy deficit is experienced at most latitudes of the atmomsphere system and stable over latitudes.
The net radiation of the earth-atmosphere system is the combination of earth surface and atmosphere system
Energy Surplus in between 0o and 40oN & SEnergy Deficit in regions higher than 40oN & S
Seasonal and latitudinal effect on Energy Budget
Summer Winter Total
Equator
Around 20o
35o-40oN&S
Polewards of about 65oN&S
surplus surplus surplus
surplus
surplus
deficit
deficit
deficit
deficit
surplus
balance
deficit
Description
Incoming solar radiation may be reflected and absorbed by clouds. Scattered and absorbed by atmosphere, reflected and absorbed by earth’s surface
Short-wave solar radiation reflected by clouds and earth’s surface may go back to space
Short-wave solar radiation scattered by atmosphere may go either to space or to the earth’s surface
Description
Radiation (both short-wave and long-wave) absorbed by clouds and atmosphere will eventually go to space or the earth’s surface in form of long-wave radiation
Radiation (both short-wave and long-wave) absorbed by earth’s surface will go back to space or atmosphere in form of log-wave radiation; or may be dissipated through latent heat loss or sensible heat loss to atmosphere
Heat transfer
Short wave radiation from the sun received by the earth leaves the atmosphere in the form of long-wave radiation and heated up the atmosphere
For the earth as a whole, the amount of short wave-radiation received will be equal to the amount of long-wave radiation lost as to keep the earth at the same temperatures in the long run
Heat transfer
The amount of short wave radiation received by the earth varies greatly along latitude and between seasons because of the earth’s spherical shape, the inclination of the axis, different amount of cloud cover and albedo of the earth’s surface
The amount of long wave radiation leaving the atmosphere at different latitude does not vary as great as the amount received and thus resulting surplus of heat in the lower latitudes and a deficiency of heat in the higher latitudes.
Heat transfer
To maintain an equilibrium, surplus heat from the low latitudes is transported to high latitude
Heat from lower altitudes is transport to higher altitudes
Both horizontal and vertical transfer are involved
Atmospheric processes such as air circulation, condensation and precipitation are involved
Heat transfer
Since air is a poor conductor, conduction is unimportant in the atmosphere, but it is important in the ground
The low viscosity of air and its consequent ease of motion makes convection the chief method of atmospheric heat transfer
Heat energy transferred by radiation becomes sensible heat only when absorbed by water vapour, carbon dioxide or ozone
Energy budget it tropical rainforest TRF
Due to high angle of incidence there is high incoming solar radiation, causing hot climate
Albedo of forest-covered surface is lowSmall variation in length of daytime leads
to little seasonal variation of incoming solar radiation producing uniform climate, small annual range of temperature and even distribution of precipitation
Energy budget it tropical rainforest TRF
Large amount of radiation absorbed by earth’s surface, causing intense convection (latent heat loss), resulting abundant precipitation throughout the whole year
About 20% incoming solar radiation reflected by clouds. Preventing extreme high temperature in daytime
Energy budget it tropical rainforest TRF
More than half of long-wave radiation from the earth’s surface absorbed by clouds and then re-radiated back to earth’s surface, keeping warm temperature in night time
Therefore, daily temperature range is also small