AL Energy Budget

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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.

Recap (What’s more)

Counter-radiation by the cloudsSensible heat transferLatent heat transfer

Assumptions

Scale: Global scaleTime: Long term trend

Division of Components

ATMOSPHERE

EARTH

Earth-atmosphere

Operation of Energy Budget

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

Income

15

11

3

216

100

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

The outgoing radiation

920

90

8

60

77

18

0

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

Annual Solar Radiation at Earth Surface

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

Global Distribution of Short Wave Radiation

Latitudinal Distribution of Annual Solar Radiation

Global Distribution of Long Wave Radiation

Global Distribution of Net Radiation

Annual Net Radiation

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

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

Relaxation of Assumptions

Relaxation of Assumptions

Illustration of the atmospheric energy budget

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

Energy budget of Tundra (Polar region)