Physical Geographyby Alan Arbogast

Chapter 5

Global Temperature Patterns

Lawrence McGlinnDepartment of GeographyState University of New York - New Paltz

Absorbed Radiation

• Stored in Earth’s land and water surfaces as sensible heat which can be felt & measured

• Stored heat can be released from surface by:– Radiation to atmosphere or to space– Conduction to atmosphere– Evaporation/Latent heat to atmosphere

Evaporation/Latent Heat

• Liquid water → Water vapor (gas)

• Latent Heat – heat energy associated with the changing state of water– Heat absorbed in evaporation– Breaks molecular bonds of liquid– Cannot be felt or measured– Released when condensation occurs

Changing State of Water

GAS

LIQUIDSOLID

Depos

ition

Hea

t Rel

ease

dSu

blim

atio

nH

eat A

bsor

bed

Vaporization

Condensation

Heat R

eleased

Heat A

bsorbed

Heat Released

Heat Absorbed

Melting

Freezing

Reflected Radiation• Depends on surface albedo and angle of

incidence (link to animation)

• Albedo – % of insolation an object reflects– High – dark surfaces– Low – light surfaces

• Angle of incidence – Sun angle– High – little reflectance– Low – high reflectance, esp. water

Solar Radiation and Earth’s Surface

Solar Radiation and Earth’s Surface

Solar Radiation and Earth’s Surface

Local Factors Influencing Air Temperature

• Urban Effect– Urban Heat Island

• Darker surfaces – less reflection• Less forest cover• Less water on surface• Heat from human energy use

The Urban Environment

Urban Heat Island

Global NET R

• Non-vegetated surfaces lose heat in one of 3 ways:– Latent heat of evaporation – energy released

as water changes state– Sensible heat – heat you can feel and

measure; convection and conduction– Ground heating and cooling – energy stored

during warm periods and released during cool periods

Radiation Budgets: Types of Heating

Pasture: Shannon, GA

Desert: Big Bend National Park, TX

Riparian Environment: Rio Grande River, TX

Global Radiation Budget

• Major variations in net radiation by latitude• Surplus vs. Deficit

•Net Radiation – difference between incoming and outgoing radiation

(Balance between incoming and outgoing radiation on Earth)

Global Radiation Budget• Seasonal variation in net radiation

Daily Insolation•Yearly pattern Variation by latitude

Heat vs. Temperature

• Heat and Temperature are not the same thing

• Heat: a form of energy that flows from one system or object to another because the two are at different temperatures

• Temperature: a measure of the average kinetic energy (motion) of individual molecules in matter

Principal Temperature Controls

• Latitude

• Altitude

• Cloud Cover

• Land-Water Heating Differences

Latitude and Temperature

• Latitude  – Affects insolation– Sun angles– Daylength

Altitude

• Altitude  – High altitude has greater daily range– High altitude has lower annual average

Cloud Cover

Land–Water Heating Differences 

• Evaporation (= latent heat)

• Transparency (= penetration of insolation)

• Specific heat (differs among objects)

• Movement (= vertical mixing)

• Ocean currents and sea surface temperatures(= spread of energy spatially)

All this leads to this important concept:Marine vs. continental effects

Land–Water Heating Differences  Continental Marine

Land Is Opaque

The Gulf Stream

Marineand Continental Climates

Local Factors Influencing Air Temperature

• Maritime vs. Continental Location

Annual Range of Surface Temp• Temp range on land vs. temp range on water

Earth’s Temperature Patterns

• Isotherm and thermal equator• January Temperature Map  

– Thermal equator movement southward– More pronounced over large continents

• July Temperature Map  – Thermal equator movement northward– More pronounced over large continents

• Annual Temperature Range Map – Continentality

January Temperatures

July Temperatures

Global Temperature Ranges