Heat transport

Water cycle

Atmospheric circulation

Processes forcing the climatic conditions

Radiation

There are four main processes of energy transport in the atmosphere:

radiation,

molecular conduction

turbulent conduction

latent heat

sensible heat

Thermal Energy

All matter is composed of atoms or molecules, which are in constant motion

Molecular or atomic motion = “thermal energy”

Heating atoms causes them to move faster, which represents an increase in thermal energy.

Temperature is a measure of thermal energy.

Radiation is the way of energy transport by electromagnetic wave moving with the speed of light. It does not demand any medium. Energy is transmitted in portions called kwantums.

wavelength × frequency = speed of light

wavelength crest

through

Energy of a wave

Energy is proportional to frequency,

and inversely proportional to wavelength

E = h

= h (c/ )

where h = Planck’s constant

In other words, waves with shorter wavelengths (or higher frequency) have higher energy

Each body with temperature higher than 0K (-273,13ºC) emits radiation to space, ie. emits an electromagnetic wave moving with the speed of light differing in wavelength, frequency and amplitude.

All bodies, with temperature greater than absolute 0,

emit radiation.

The rate at which something radiates and absorbs

energy depends strongly on its surface

characteristics, such as color, texture, moisture and

temperature.

There is a group of bodies called black bodies. The

rate at which they radiate energy depends only on

their temperature. They are perfect absorber of

radiation (absorb all radiation that strikes them) and

a perfect emitter (emit the maximum radiation

possible at their temperature).

Blackbody Radiation

Blackbody radiation—radiation emitted by a body that at all wavelengths emits (or absorbs) energy in the amount described by law of Planck.

Law of Planck

Basic Laws of Radiation

1) All objects emit radiant energy.

Basic Laws of Radiation

1) All objects emit radiant energy.

2) Hotter objects emit more energy than colder objects.

Basic Laws of Radiation

1) All objects emit radiant energy.

2) Hotter objects emit more energy than colder objects. The amount of energy radiated is proportional to the temperature of the object raised to the fourth power.

Basic Laws of Radiation

1) All objects emit radiant energy.

2) Hotter objects emit more energy than colder objects. The amount of energy radiated is proportional to the temperature of the object raised to the fourth power.

This is the Stefan Boltzmann Law

E = T4

E = flux of energy (W/m2)T = temperature (K) = 5.67 x 10-8 W/m2K4 (a constant)

Basic Laws of Radiation

1) All objects emit radiant energy.

2) Hotter objects emit more energy than colder objects (per unit area). The amount of energy radiated is proportional to the temperature of the object.

3) The hotter the object, the shorter the wavelength () of emitted energy.

Basic Laws of Radiation

1) All objects emit radiant energy.

2) Hotter objects emit more energy than colder objects (per unit area). The amount of energy radiated is proportional to the temperature of the object.

3) The hotter the object, the shorter the wavelength () of emitted energy.

This is Wien’s Law

max 3000 m T(K)

Stefan-Boltzmann law

E = T4

E = flux of energy (W/m2)T = temperature (K) = 5.67 x 10-8 W/m2K4 (a constant)

Wien’s law

max 3000 m T(K)

The amount of energy emitted by the black body at wavelength is depends only on the object temperature and is described by Planck's law:

1e

1hc2E kT/hc5

2

k Bolzmann's constant (k=1,38·10-23J/K) T temperature in Kelvin scale

c – speed of light (3,0·108m/s), h - Planck's constant (h=6,63·10-34J·s),

solar spectrum

Earth's spectrum

We can use these equations to calculate properties of energy radiating from the Sun and the Earth.

6,000 K 300 K

T

(K)

max

(m)Part of

spectrum

E

(W/m2)

Sun 6000

Earth 300

T

(K)

max

(m)Part of

spectrum

E

(W/m2)

Sun 6000 0.5

Earth 300 10

Wien’s law: max 3000 m T(K)

T

(K)

max

(m)Part of spectrum

E

(W/m2)

Sun 6000 0.5 Visible(yellow?)

Earth 300 10 infrared

T

(K)

max

(m)Part of

spectrum

E

(W/m2)

Sun 6000 0.5 Visible(green)

7 x 107

Earth 300 10 infrared 460

Stefan-Boltzmann law: E = T4

0.01 0.1

1 10

100 1000wavelength

en

erg

y

Sun

Earth

Hotter objects emit more energy than colder objects E=σT4

0.01 0.1

1 10

100 1000wavelength

en

erg

y

Sun

Earth

Hotter objects emit at shorter wavelengths.

max = 3000/T

Outgoing Longwave Radiation (OLR) Anomalies

Wetter-than-average conditions (blue shading)

Drier-than-average conditions (orange/red shading)

From October – December 2011, variability in OLR anomalies (focused mostly over the Indian Ocean and Maritime Continent) was associated with the MJO.

Since April 2010, negative OLR anomalies have been observed near the Maritime Continent and positive OLR anomalies have prevailed over the western and central Pacific.

Recently, eastward propagation of negative OLR anomalies is evident in association with the MJO.

Longitude

Time

Climate Prediction Center / NCEP

UV

visible light

infrared radiation

wavelength

Intensity of solar radiation at the upper boundary of the atmosphere is called solar constant and amounts on average 1353 W/m2.

Solar constant is not perfectly constant. The elliptical path of the Earth around the Sun brings the Earth closer to the Sun in January (147 mln km in aphelium) than in July (152 mln km in perihelium). From this reason the changes in solar constant during the year are about 3.5%.

Since 1978 the remote sensing has been measured. It appears that the solar constant is also changing with solar activity. These changes did not exceed the level of 0.08% during the 30 years of measurements.

In very long time scale (thousands of years) the orbital parameters of the Earth path around the Sun cause some changes in solar constant. The intensity of solar radiation is also changing in the long history of the Earth. 3.5 billions of years ago the Sun emitted only 70 % of radiation it is emitting today.

Solar radiation is emitted in each direction equally. Because the distance from the Sun to the Earth is really huge than the radiation reaching the surface is parallel. The amount of energy reaching the earth surface in the time unit is called intensity of direct solar radiation.Radiation that strikes a surface at an angle is spread over a larger area than the radiation that strikes the surface directly.

sinh' II

1. All objects with temperature above absolute zero emit

radiation.

2. The higher the object temperature, the greater the

amount of radiation emitted per unit surface area and

the shorter the wavelength of maximum emission.

3. The Earth absorbs solar radiation only during the

daylight hours; however, it emits infrared radiation

continuously, both during day and at night.

4. The Earth’s surface behaves as a black body, making it

a much better absorber and emitter of radiation than is

the atmosphere

absorption and emission

reflection

scattering

In the atmosphere the radiation can be:

scattered,

absorbed

reflected.

When sunlight strikes a very small objects such as air molecules and dust particles the light itself is deflected in all directions – forward, sideward and backward. It is called scattering. Scattering on a tiny particles was firstly described by English scientist lord Rayleigh (1842-1919) and is called a Rayleigh scattering.

4

Ii kiλ - intensity of scatttered radiation of wavelenght λ,

Iλ - intensity of direct radiation of wavelenght λ,

k – coefficient of scattering.

Absorption

During the absorption process, the infrared radiation is converted into internal energy. Gases in our atmosphere are selective absorbers. Ozone, for example, absorbs UV radiation, especially at wavelengths between 0.2 and 0.3 μm, and an infrared radiation at 9.6 V μm.Molecular oxygen absorb UV radiation below 0.2 μm. Water vapor and carbon dioxide absorb energy in the infrared wavelengths.

ABSORPTION in the ATMOSPHERE

infraredvisible

During the absorption process, the absorbed radiation is converted into internal energy. Gases in our atmosphere are selective absorbers. Ozone, for example, absorbs UV radiation, especially at wavelengths between 0.2 and 0.3 μm, and an infrared radiation at 9.6 V μm.Molecular oxygen absorb UV radiation below 0.2 μm. Water vapor and carbon dioxide absorb energy in the infrared wavelengths.

Absorption of radiation by gases in the atmosphere

gas absorption wavelenghts

oxygen O2 0,01-0,2 m

ozone O3 0,2-0,3 m, 9,6 m

water vapor H2O 0,81 m, 0,93 m, 1,13 m, 1,37-2,66 m, 6,26m, 9-34 m

carbon dioxide CO2 2,3-3,0 m, 4,2-4,4 m, 12,5-16,5 m

White or shiny objects reflect sunlight from their surface.An object that reflects a great deal of radiation of sunlights absorbs (and emits) very little. The percent of radiation returning from the surface compared to the amount of radiation stiking it is called the albedo of the surface.

surface or object albedo surface or object albedo

fresh snow 75-95%

grassy field 10-30%

cloud (thick) 60-90%

dry, plowed field 5-20%

cloud (thin) 30-50%

water 10%

ice 30-40%

forest 3-10%

sand 15-45%

Earth surface radiation balance

efEAiIR )1()sinh(

zwzef EEE

income outcome

direct radiation

direct radiation falling on flat surface

scattered radiation

total radisation falling on flat surface

solar radiation absorbed by the Earth surface

radiation emitted by the Earth

radiation transmitted downward

efective radiation of the Earth

Daily course of temperature and balance of radiation

The Earth annual radiation balance and temperature course

Influence of ground cover type on heat balance

GLEHQ

sensible heatused for warming of the air

net radiation input

latent heatused for evapotranspiration

exchange with the ground

Types of heat balance

Differences in heating of land and water surfaces

transparency type of conductivity (turbulent or no) transpiration losses specific heat

comparison of maritime and continentals climates

the temperature rangethe shift of maximum temperature

Questions and problems:

1. Describe some of the transformations energy goes through as water evaporates from the ocean.2. How does the temperature of the object influence the radiation that it emits?3. If the Earth's surface continually radiates energy, why it does not became colder and colder?4. In the northern latitudes the oceans are warmer in summer than they are in winter. In which season do the oceans lose heat most rapidly to the atmosphere by conduction? Explain.5. If all of the greenhouse gases were removed from the Earth's atmosphere, how would this influence the Earth's average temperature? Explain

How to explain glaciations?

Tjeerd van AndelNowe spojrzenie na starą planetę, PWN, 1997Chapter 5

8th November 2012