ClimateClimate

ContinuedContinued

Layers of the AtmosphereLayers of the Atmosphere

• The atmosphere has 4 distinct layers, The atmosphere has 4 distinct layers, each with a particular set of properties.each with a particular set of properties.

• Layers are:Layers are:– divided by temperature patterns;divided by temperature patterns;– vary in thickness;vary in thickness;– are separated by interfaces with names are separated by interfaces with names

ending in “pause”.ending in “pause”.

Layers of the AtmosphereLayers of the Atmosphere

• The 4 layers of the atmosphere The 4 layers of the atmosphere are:are:

– ThermosphereThermosphere• mesopausemesopause

– MesosphereMesosphere• stratopausestratopause

– StratosphereStratosphere• tropopausetropopause

– TroposphereTroposphere

TroposphereTroposphere

• Closest to the surface of the Earth• Temperature drops as you rise (6.4oC/km)• Composition is 78% nitrogen, 20%

oxygen, 2% other gases (Ar,CO2,Ne,He)• Contains most of the dust and water vapor• Most weather occurs in this layer

TropopauseTropopause

StratosphereStratosphere

• Layer above troposphere• Temperature rises as you rise• Very little weather

StratopauseStratopause

MesosphereMesosphere• Layer above the stratosphere• Temperature drops (to -90oC) as you rise

Mesosphere Clouds

MesopauseMesopause

• Located where the temperature stops falling in the mesosphere.

ThermosphereThermosphere

• The outer, upper layer of the atmosphere• Temperatures rise to 1000oC as you rise• Very little matter in this layer• High temperatures due to x-rays and UV

Atmosphere Affects Atmosphere Affects InsolationInsolation

• AbsorptionAbsorption: the stratosphere absorbs most of the ultraviolet radiation while carbon dioxide and water vapor in the troposphere absorb most of the infrared radiation.

• ReflectionReflection: clouds reflect approximately 25% of incoming insolation.

Atmosphere Affects Atmosphere Affects InsolationInsolation

• ScatteringScattering: aerosolsaerosols (water droplets, water droplets, ice crystals, pollutants and dustice crystals, pollutants and dust) in the atmosphere cause random reflection of insolation. This scattering of insolation increases as levels of aerosols increases. As scattering increases insolation to the surface decreases.– Ex: volcanic eruptions increase aerosols

and greatly reduce insolation to the surface.

Atmosphere Affects Atmosphere Affects InsolationInsolation

• Energy conversionEnergy conversion: some energy is converted to potential energy (latent latent heatheat) by the evaporation of water and the melting of ice and snow. This reduces the amount of energy available to heat an area and also increases the amount of water vapor in the air which also reduces the insolation available making for lower temperatures.

• Energy is also radiated back into Energy is also radiated back into space in the form of heatspace in the form of heat (infraredinfrared).

SurfacesSurfaces

• Land surfaces heat up and cool down more rapidly than water surfaces.

• Since good absorbers are also good radiators, the land radiates heat to the air above more rapidly than water does.

– So air above the land heats and cools more quickly than air over water.

Terrestrial RadiationTerrestrial Radiation• Terrestrial Terrestrial

radiationradiation is electromagnetic energy given off by the Earth’s surface.– This is in the form

of infrared infrared radiationradiation.

The Greenhouse EffectThe Greenhouse Effect

• The process that allows short-wave energy to be transmitted through the atmosphere, but which reflects and captures reradiated long wave infrared energy is known as the greenhouse effectgreenhouse effect.

Radiative Balance vs. TimeRadiative Balance vs. Time

• Radiative balance occurs when the incoming energy equals the outgoing energy.

• Over long-term periods the Earth seems to be in radiative balance

• Over short-term periods the Earth does not seem to be in radiative balance.

The Water BudgetThe Water Budget

• EvapotranspirationEvapotranspiration refers to all the moisture released into the atmosphere by both evaporation and transpiration.

• A water budgetwater budget is a monthly account of what happens to all the water in a particular location over the course of a year.

Water Budget Income and Water Budget Income and ExpensesExpenses

• “IncomeIncome” in a water budget is the amount of precipitationprecipitation.

• “ExpensesExpenses” in a water budget is the potential evapotranspirationpotential evapotranspiration.– Potential evapotranspirationPotential evapotranspiration is the amount

of water that wouldwould evaporate or transpire ifif the water were availableavailable.• Therefore potential evapotranspiration is

highest in the summer (when it is hottest), lowest in winter (when it is coldest).

• Large vegetated areas give off more evapotranspiration.

Factors Affecting Water Factors Affecting Water BudgetsBudgets

• Climate affects a water budgetClimate affects a water budget: since evapotranspiration rates are largely dependent upon the sun, the factors determining climate (temperature and humidity) also affect water budgets.– Arid climateArid climate = total annual precipitation precipitation

is lessis less than potential evapotranspiration.– Humid climateHumid climate = total precipitation is precipitation is

moremore than potential evapotranspiration.

Stream DischargeStream Discharge

• Stream dischargeStream discharge is the amount of water passing a given point in a stream during a given time. – Areas with surplus moisture usually have

large amounts of runoff into streams.– Greater amounts of runoff means greater

stream discharge.– During drydry, or deficitdeficit, periods when runoff

diminishes, streams take water from the ground water supply: this is called base base flowflow.