Radiation balance

between absorbed and emitted by a body radiation is called

balance of radiative energy (radiation balance – R) of the body.

We know sufficiently well about the R of the Earth surface and R of the Earth as a whole planet. However, we know a little about the radiation balance of separate layers of the atmosphere.

soil and the surface layer of the atmosphere.
Processes of fog

and frost formation.
Air mass transformation.

Radiation balance varies depending on latitude, time of the year and day, and weather conditions.

Radiation balance can be calculated for various time intervals: minutes, hours, days, weeks etc.
It can be positive ( income exceeds outlay) and negative (the body emits more energy than absorbs)

Radiation balance is subject for annual and diurnal variations.

Earth surface.

April

June

October
An important feature of the radiation balance is its

transfer via 0. Usually, it happens at the time when Sun altitude reaches 10 -15°. In case of snow cover existence it occurs at the Sun altitude 20 - 25°. This means that the time interval with positive radiation balance becomes much shorter.

For a location at 60°N latitude

the radiation balance depends on latitude and type of underlying

surface.
Tropical area: radiation balance is always positive.
Antarctic area: radiation balance is always negative due to large value of the surface albedo.
At 60° latitude: radiation balance is positive 6 – 8 months a year.
In arctic area there are some places where radiation balance (average for a year) is positive. It is valid for the places with snow and ice free surfaces for at least 2 months. The Sun shines here 24 hours at summer months.
Question: Where radiation balance is larger on ocean or on land at the same altitude and weather conditions?
Answer: On ocean, since water surface albedo is less than that of land

and “b” depends on albedo of the underlying surface.
Cloudiness impact
When

R>0, cloudiness causes the net and effective radiation decrease. But the net radiation decrease is much stronger. Therefore, the radiation balance decreases at cloudiness condition.
When R<0, cloudiness causes the effective radiation decease and, hence, decrease of radiation balance absolute value.
Conclusion: cloudiness always decreases the radiation balance absolute value

radiation that goes into the space

values are negative over whole globe.

the balance of radiative energy in a vertical column including

active layer of soil ( water) and the atmosphere.

Outgoing part

Incoming part

Every unit of time the Earth receives the amount of SR equal to the product of the solar constant by the area of the Earth cross section i. e.

Due to Earth rotation this energy is distributed over the all surface of the globe that is

Near equator RE>0 over the whole year. In the middle latitudes RE>0 is observed only in summer.

diminishes U∞ value
U∞
RE
At nights, when ,
At clear sky
At cloudy

weather