Atmospheric temperatureAtmospheric temperature

Review of last lectureReview of last lecture

EarthEarth’’s energy balance at the top of the s energy balance at the top of the atmosphere and at the surface. What percentage of atmosphere and at the surface. What percentage of solar energy is absorbed by the surface?solar energy is absorbed by the surface?

Atmospheric influences on radiation (3 ways)Atmospheric influences on radiation (3 ways) What cause the greenhouse effect? What are the What cause the greenhouse effect? What are the

major greenhouse gases? Why is methane major greenhouse gases? Why is methane important? important?

The three types of atmospheric scattering. What The three types of atmospheric scattering. What causes the blue sky? Why causes the reddish-causes the blue sky? Why causes the reddish-orange sunsets? orange sunsets?

Sensible heat flux (dry flux from warm to cold Sensible heat flux (dry flux from warm to cold regions) and latent heat flux (wet flux from wet to regions) and latent heat flux (wet flux from wet to dry regions). Both proportional to surface wind dry regions). Both proportional to surface wind speedspeed

Atmospheric ThicknessAtmospheric Thickness No defined top to the atmosphereNo defined top to the atmosphere The atmosphere is very shallow—and is The atmosphere is very shallow—and is

less than 2% of the Earth’s thicknessless than 2% of the Earth’s thickness

Over 90% ofatmosphere inthe lowest 16km& is where nearlyall weather occurs

Temperature BasicsTemperature Basics TemperatureTemperature – measure of average kinetic energy – measure of average kinetic energy

(motion) of individual molecules in matter(motion) of individual molecules in matter Three temperature scales (units): Kelvin (K), Celsius (C), Three temperature scales (units): Kelvin (K), Celsius (C),

Fahrenheit (F)Fahrenheit (F) All scales are relativeAll scales are relative degrees F = degrees F = 99⁄⁄55 degrees C + 32 degrees C + 32 degrees K = degrees C + 273.15degrees K = degrees C + 273.15

Temperature LayersTemperature Layers

Due to surface heating (Longwave, Latent heat, Sensible heat)

Due to ozone absorption of sunlight

Due to Solar winds, Cosmic rays

Decreasing rate w/ height (Lapse rate):6.5 oC/km

Sub-layers in troposphereSub-layers in troposphere

Definition of the Definition of the boundary layerboundary layer: "that part of the : "that part of the troposphere that is directly influenced by the presence of troposphere that is directly influenced by the presence of the earth's surface and responds to the earth's surface and responds to surface forcingssurface forcings (friction (friction and heating) with a time scale of about an hour or less.and heating) with a time scale of about an hour or less.””

About 1 km deep. Often associated with turbulence.About 1 km deep. Often associated with turbulence.

Space shuttle Endeavour straddles Space shuttle Endeavour straddles mesosphere and stratospheremesosphere and stratosphere

An artistAn artist’’s views view

VideoVideo Weather: Weather: WindWind

Horizontal distribution of Horizontal distribution of temperaturetemperature

IsothermsIsotherms – maps, connect lines of equal temperature – maps, connect lines of equal temperature

Seasonal variation of surface air Seasonal variation of surface air temperaturetemperature

Principal Controls on Temperature   Principal Controls on Temperature   

1.1. Latitudinal variations in net radiationLatitudinal variations in net radiation

2.2. Land-Water ContrastsLand-Water Contrasts

3.3. Atmospheric CirculationAtmospheric Circulation

4.4. Ocean CurrentsOcean Currents

5.5. AltitudeAltitude

6.6. Local EffectsLocal Effects

• tropic-to-tropic – energy surplus• poles – energy deficits• ~ 38o N/S – balance

• imbalance of net radiation at surface Equator/Tropics vs. high latitudes

• drives global circulation• agents: wind, ocean currents, weather systems

Controls on temperature 1. Latitudinal Variations in Net Radiation

Daily/Seasonal Radiation Patterns

• insolation peak vs. temperatureinsolation peak vs. temperature• daily lagdaily lag• seasonal lagseasonal lag• Lag is function of type of surface, wetness, wind, etcLag is function of type of surface, wetness, wind, etc

Seasonal variation of surface Seasonal variation of surface radiationradiation

Seasonal variation of surface energy Seasonal variation of surface energy budgetbudget

Storage change = net radiation - latent heat flux - sensible heat flux

• T decreases poleward• larger T gradient in winter• isotherms shift seasonally• NH steeper T gradient • T over land > water in summer

Seasonal Seasonal Temp Temp DistributioDistributio

nsns

Controls on temperature 2. Land-water contrasts

Surface influences heating: • Heat Capacity – water > land… (water takes longer heat/cool)• Mixing – fluids can be physically mixed• Transparency – greater penetration (distributed over greater volume)• Evaporation – consumes large amount of energy – big over water

Temperature Ranges (Summer minus Winter)Large over land, small over ocean

• large scale circulation patterns resulted from pressure differences (gradients)• generates winds move warm/cold air around affects temperature• influences cloud cover

Controls on temperature 3. Atmospheric circulation

Controls on temperature 4. Ocean currents

Infrared Satellite image of the Gulf Stream

Red/orange = 25-29oC

Yellow/green = 17-24oC

Blue = 10-16oC

Purple = 2-9oC

• Temperature decreases with increasing altitude ground acts as heat source

Controls on temperature Controls on temperature 5. Altitude5. Altitude

• slope orientation: North vs South-facing slopes temperature/moisture regimes vegetation

Controls on temperature Controls on temperature 6. Local effects6. Local effects

forested vs open fields

SummarySummary Thickness of the atmosphere: less than 2% of EarthThickness of the atmosphere: less than 2% of Earth’’s s

thicknessthickness Definition of temperature. 3 units. Definition of temperature. 3 units. Vertical distribution of temperature: 4 layers, what Vertical distribution of temperature: 4 layers, what

separate them?separate them? Horizontal distribution of temperature. Horizontal distribution of temperature. 6 factors.6 factors.

1.1. Latitudinal variations in net radiationLatitudinal variations in net radiation

2.2. Land-Water ContrastsLand-Water Contrasts

3.3. Atmospheric CirculationAtmospheric Circulation

4.4. Ocean CurrentsOcean Currents

5.5. AltitudeAltitude

6.6. Local EffectsLocal Effects