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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
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