The Layered AtmosphereThe Layered Atmosphere

The Earth's The Earth's atmosphere atmosphere

contains contains several several

different layers different layers that can be that can be

defined defined according to air according to air

temperaturetemperature

TroposphereTroposphere

• According to temperature, the atmosphere contains four different layers (Figure 7b-1). The first layer is called the troposphere.

• The depth of this layer varies from about 8 to 16 kilometers.

• Greatest depths occur at the tropics where warm temperatures causes vertical expansion of the lower atmosphere. From the tropics to the Earth's polar regions the troposphere becomes gradually thinner. The depth of this layer at the poles is roughly half as thick when compared to the tropics.

• Average depth of the troposphere is approximately 11 kilometers as displayed in Figure 7b-1

StratosphereStratosphere

• Above the tropopause is the stratosphere.

• This layer extends from an average altitude of 11 to 50 kilometers above the Earth's surface.

• This stratosphere contains about 19.9 % of the total mass found in the atmosphere. Very little weather occurs in the stratosphere. Occasionally, the top portions of thunderstorms breach this layer.

• The lower portion of the stratosphere is also infuenced by the polar jet stream and subtropical jet stream. In the first 9 kilometers of the stratosphere, temperature remains constant with height.

StratosphereStratosphere• A zone with constant temperature in

the atmosphere is called an isothermal layer.

• From an altitude of 20 to 50 kilometers, temperature increases with an increase in altitude. The higher temperatures found in this region of the stratosphere occurs because of a localized concentration of ozone gas molecules.

• These molecules absorb ultraviolet sunlight creating heat energy that warms the stratosphere. Ozone is primarily found in the atmosphere at varying concentrations between the altitudes of 10 to 50 kilometers.

• This layer of ozone is also called the ozone layer . The ozone layer is important to organisms at the Earth's surface as it protects them from the harmful effects of the sun's ultraviolet radiation. Without the ozone layer life could not exist on the Earth's surface.

Stratopause & MesosphereStratopause & Mesosphere

• Separating the mesosphere from the stratosphere is transition zone called the stratopause.

• In the mesosphere, the atmosphere reaches its coldest temperatures (about -90° Celsius) at a height of approximately 80 kilometers.

• At the top of the mesosphere is another transition zone known as the mesopause.

ThermosphereThermosphere

• The last atmospheric layer, as defined by vertical temperature change, has an altitude greater than 80 kilometers, and is called the thermosphere.

• The thermosphere is the hottest layer in the atmosphere.

• Heat is generated from the absorption of solar radiation by oxygen molecules.

• Temperatures in this layer can reach 1300 to 1800° Celsius.

+25 direct

Clouds Absorbed

+3 units

-31 units (Albedo)

Reflected back to space

Scattering

SUN +100

Energy absorbed in

Troposphere+18 units( gases ,dust)

-7

-21

-3

+10+10

Total energy absorbed at surface = +45 units

Energy absorbed in

Stratosphere +3 unitsOzone

Total energy received

-3 units of UV from ozone layer

Energy radiated to space –Total = 69 units

-21 units from the atmosphere heat input

-8 units of direct heat loss from the earth’s surface

-14 units from the greenhouse effect

Energy from Long wave radiation= 46 units +

Non radiative exchanges = 23 units

Long wave Radiation Exchanges

Long wave radiation itself accounts for 46 units of the total 69 units derived from the short wave budget

Energy gained and lost by the greenhouse effect: Total –14 units

Long wave radiation: -110 units

Downward radiation+96 units

The Green house effect

Long wave radiation exchange

Non Radiative exchanges

Convective (turbulent) transfer- 4 units

Latent heat transfer (evaporation)

-19 units

Non radiative exchanges

This accounts for the remaining total 23 units

Energy Budget variation with LatitudeEnergy Budget variation with Latitude

Equator 0o

40o N

40o S

90o N

90o S

GAIN

This means there is a POSITIVE HEAT balancewithin the tropics

And a NEGATIVE HEAT BALANCE both at highlatitudes (polar regions)

TWO major TRANSFERS OF HEAT take place toprevent the tropical areas from overheating

Simple Model of Global Simple Model of Global CirculationCirculation

Three Cell Model of Global Three Cell Model of Global CirculationCirculation

NorthernHemisphere

SouthernHemisphere

Diagram showing the Tricellular Model

Depressions – a mid –latitude vortexDepressions – a mid –latitude vortex

Depressions – a mid –latitude Depressions – a mid –latitude vortexvortex

Depressions – a mid –latitude Depressions – a mid –latitude vortexvortex

OriginOrigin

MaturityMaturity

OcclusionOcclusion

The passage of a mature The passage of a mature depression across the United depression across the United

Kingdom Kingdom

AnticyclonesAnticyclones

Air-mass types Air-mass types

•There are four main types of air mass:

• Tropical continental (Tc) • Tropical maritime (Tm) • Polar continental (Pc) • Polar maritime (Pm) • And two further sub-divisions: • Arctic maritime (Am) • Returning polar maritime (rPm)

The Daytime Energy Budget (small scale) Energy at surface (local scale during daylight)

=

Incoming Solar Radiation

-

Reflected energy from clouds and surface + Surface absorption + latent heat + Sensible heat transfer (convection currents) + Long wave radiation balance

The Daytime Energy Budget (small scale)

High Sun 13%

Low Sun5%

Energy lost to Space

Greenhouse gas

Long Wave RadiationNet Radiation Balance

Evaporation Latent energy

Cloud Type

Surface Absorption of energy

Reflection from ground. Albedo

Ground FrostGround Frost

Walled GardenWalled Garden

Smudge PotsSmudge Pots

• Tablas Creek uses frost-prevention fans in early spring to protect against radiation frosts, where cold air settles near the surface

Problems of IceProblems of Ice