Effective radiation

Сентябрь 3, 2022

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Effective radiation

Содержание

2. Difference between Earth’s surface own radiation B0 and absorbed by the surface the long wavelength atmospheric
3. In some rare cases, the effective radiation may turn out to be negative (B* When? -
4. Effective radiation and water vapor in the atmosphere Effective radiation greatly depends on: the water vapor
5. Application of Angstrem’s formula Here, e1 is water vapor pressure at the level z1, are empirical
6. Let’s denote A=0,18 and D=0,25 (dimensionless quantities); c=0,95 if e1 in hPa There is also well
7. Cloudiness impact on counter and effective radiation Effective radiation depends upon following factors Cloudiness thickness Cloudiness
8. Counter (earthward) flux from the cloud layer Z cloud base height The energy loss when passing
9. At overcast condition This formula suggests that at overcast ER decreases since the quantity in brackets
10. Let’s transform the ratio Decomposing into raw and restricting our self with only first member, we
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Difference between Earth’s surface own radiation B0 and absorbed by the

surface the long wavelength atmospheric back radiation is called effective radiation of the Earth surface.

Usually

Therefore

and

It means that through the long wave radiation the surface always looses the energy.

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In some rare cases, the effective radiation may turn out to

be negative (B*<0)
When?

- may arise at clear nights, the surface becomes very cold.

Effective radiation has an important bearing
on the temperature regime of the Earth surface.
It plays a significant role in radiation frost and
fog formation and in snow melting.

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Effective radiation and water vapor in the atmosphere
Effective radiation greatly depends

on:
the water vapor content in the atmosphere
presence of cloudiness. It decreases with increase of the water vapor content.

Increase of humidity results in increase of BA value, and, hence, decrease of B* value.

Air temperature at the level z1

Absorption coefficient

Value z1 is arbitrary chosen quantity, it can be equal to 2 meters. Coefficient “a” specifies emissivity of the atmosphere, depends on humidity, amount and altitude of the cloudiness.
The increase of water vapor pressure and cloud amount results in coefficient “a” growth up.

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Application of Angstrem’s formula
Here, e1 is water vapor pressure at the

level z1, are empirical constants.

Combining formulas

We obtain

Effective radiation in cloud free atmosphere

Let’s add

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Let’s denote
A=0,18 and D=0,25 (dimensionless quantities); c=0,95 if e1 in hPa
There

is also well known Brent’s formula

“e” in hPa

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Cloudiness impact on counter and effective radiation
Effective radiation depends upon following

factors
Cloudiness thickness
Cloudiness altitude
Cloudiness form
Cloud amount
To understand the essence of the impact, an example will be considered.
Initial conditions are: overcast, cloud base height is a few hundred meters.
Notation: T0 is the surface temperature, T1 is air temperature in shelter, Tk is air temperature at the cloud base.
At these conditions: ; ; within the layer from the surface up to the cloud base.

Numerous influencing factor combinations make theoretical approach to the problem to be very complicated or even not possible.

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