The Layered Atmosphere The Earth's atmosphere contains several different layers that can be defined according to air temperature temperature

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

Stratosphere Above the tropopause is the stratospherestratosphere. 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 streamstream. In the first 9 kilometers of the stratosphere, temperature remains constant with height.

Stratosphere A zone with constant temperature in the atmosphere is called an isothermal layerlayer. 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 & Mesosphere Separating the mesosphere from the stratosphere is transition zone called the stratopausestratopause. 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 mesopausemesopause.

Thermosphere The last atmospheric layer, as defined by vertical temperature change, has an altitude greater than 80 kilometers, and is called the thermospherethermosphere. 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) Total energy absorbed at surface = +45 units Energy absorbed in Stratosphere +3 units Ozone

-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

Energy gained and lost by the greenhouse effect: Total –14 units Long wave radiation: units Downward radiation +96 units

Non Radiative exchanges Convective (turbulent) transfer - 4 units Latent heat transfer (evaporation) -19 units

Energy Budget variation with Latitude

Equator 0 o 40 o N 40 o S 90 o N 90 o S GAIN

Simple Model of Global Circulation

Three Cell Model of Global Circulation

Northern Hemisphere Southern Hemisphere Diagram showing the Tricellular Model

Depressions – a mid –latitude vortex

Origin

Maturity

Occlusion

The passage of a mature depression across the United Kingdom

Anticyclones

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)

High Sun 13% Low Sun 5% Energy lost to Space Greenhouse gas Long Wave Radiation Net Radiation Balance Evaporation Latent energy Cloud Type Surface Absorption of energy Reflection from ground. Albedo

Ground Frost

Walled Garden

Smudge Pots

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

Problems of Ice