Chapter 4: Insolation and Temperature

The Impact of Temperature on the Landscape All living things influenced by temperature Adaptation to temperature extremes Temperature affects human-built landscape Temperature affects inorganic landscape components Soil and bedrock exposure Figure 4-1a & 4-1b

Energy, Heat, and Temperature Energy: ability to do work Forms of energy Kinetic – energy of movement Chemical, Potential, Nuclear, etc. Temperature Heat Movement of atoms Temperature: Measurement of heat Temperature scales Celsius Fahrenheit Kelvin Figure 4-2

Energy, Heat, and Temperature The Sun Primary source of energy for Earth’s atmosphere Properties of Sun Average size star Nuclear fusion Magnitude of Sun’s energy Energy spreads as it leaves the Sun Travels through voids in space without loss of energy Figure 4-3

Energy, Heat, and Temperature Figure 4-4 Electromagnetic (EM) energy EM spectrum Wavelength Distance between two wave crests 3 important areas of EM spectrum Visible radiation Ultraviolet radiation Too short to be seen by the human eye Infrared radiation Figure 4-5

Energy, Heat, and Temperature Insolation Incoming solar radiation Shortwave energy Terrestrial Energy Longwave energy “Earth’s” energy Figure 4-16

Basic Heating and Cooling Processes in the Atmosphere Radiation When objects emit EM energy AKA Heat energy emitted from a body Warmer objects radiate more effectively Warmer objects emit at shorter wavelengths Figure 4-6

Basic Heating and Cooling Processes in the Atmosphere Absorption Body absorbs radiation Good radiator, good absorber Reflection Objects repel electromagnetic waves Opposite of absorption Figure 4-7

Basic Heating and Cooling Processes in the Atmosphere Scattering Deflection of light waves by molecules and particles Transmission Electromagnetic waves pass completely through a medium Sunsets Figure 4-9

Basic Heating and Cooling Processes in the Atmosphere Greenhouse effect Some atmospheric gases transmit shortwave radiation, but not Earth’s longwave radiation Earth radiation held in by atmosphere Atmospheric blanket Figures 4-11 & 4-12

Basic Heating and Cooling Processes in the Atmosphere Conduction Transfer of heat energy across a medium Energy moves from molecule to another one without changing molecular positions AKA direct heat transfer by contact Molecules become agitated, then vibrate & collide with cooler molecules, transferring heat energy Figure 4-13

Basic Heating and Cooling Processes in the Atmosphere Convection Heat transfer by vertical circulation in a moving substance Vertical convection cell Warm air gains heat, expands & rises Cool air loses heat, contracts & sinks Advection Horizontal transfer of heat in a moving fluid AKA wind Figure 4-14

Radiation, Conduction & Convection Operating Simultaneously

Basic Heating and Cooling Processes in the Atmosphere Adiabatic Cooling and Warming Change in pressure & thus temperature of rising or descending air Adiabatic cooling Air rises and expands, molecular collisions decrease, so temperature decreases Adiabatic warming Air sinks and compresses, collisions increase so temperatures increase Figure 4-15

Basic Heating and Cooling Processes in the Atmosphere Latent heat Heat released or absorbed during a phase change AKA “hidden heat” since latent heat is not felt Evaporation: liquid water is converted to water vapor Cooling process Condensation: water vapor is converted to liquid water Warming process

The Heating of the Atmosphere Balance between shortwave incoming solar radiation & outgoing longwave solar radiation Albedo The higher the albedo, the more radiation the object reflects Figure 4-16

The Heating of the Atmosphere: Global Energy Budget Energy in = Energy out Figure 4-17

The Heating of the Atmosphere: Global Energy Budget Earth does not distribute heat evenly through space & time Cause of weather and climate

Variations in Heating by Latitude and Season Angle of incidence Angle the Sun’s rays strike Earth’s surface The higher the angle, the more intense the radiation Figure 4-18

Variations in Heating by Latitude and Season Atmospheric obstructions Clouds, haze, particulates, etc. decrease insolation Figure 3-4 Figure 4-20

Variations in Heating by Latitude and Season Day length The longer the day, the more insolation is received Figure 4-19

Variations in Heating by Latitude and Season Latitudinal radiation balance and the world distribution of insolation Belt of max solar energy that moves through the tropics following the Sun’s direct rays Figure 4-21

Land and Water Contrasts Land heats and cools more rapidly than water due to: Specific heat Transmission Mobility Evaporative cooling Figure 4-23

Land and Water Contrast Implications Oceans = more moderate climates Hottest & coldest places on Earth are interiors of continents N. (land) vs. S. (water) Hemisphere Figure 4-24

Mechanisms of Heat Transfer Need heat transfer to prevent constant warming at tropics & cooling at poles Circulation patterns in atmosphere and oceans transfer heat

Mechanisms of Heat Transfer 2 mechanisms move heat poleward in both hemispheres, driven by latitudinal imbalance of heat Atmospheric circulation (Ch 5) Oceanic circulation Direct relationship between atmospheric and oceanic circulation Air blowing over the ocean creates major surface ocean currents Heat energy stored by oceans affects atmospheric circulation

Mechanisms of Heat Transfer Northern and southern variations Near N. Hemisphere pole, landmasses lie so close that little flow can enter the Arctic Ocean In S. Hemisphere, little land mass allows for constant westward belt of ocean circulation called West Wind Drift Southern Ocean (AKA the 5th Ocean)

Mechanisms of Heat Transfer Temperature patterns Poleward currents transfer warm water poleward Equatorial currents transfer cool water equatorward Figure 4-25

Mechanisms of Heat Transfer Figure 4-26 Rounding out the pattern NW portions of N. Hemisphere receive cool water from Arctic Ocean Water pulled away from western coasts of continents = upwelling Deep ocean circulation Global conveyor belt Tied to short-term climate change

Vertical Temperature Patterns Environmental lapse rate Normal vertical temperature gradient Average lapse rate 6.5°C/km or 6.5°C/1000m) Temperature inversions Surface inversions Upper air inversions Figures 4-27 & 4-28

Global Temperature Patterns Global temperature maps Seasonal extremes January & July BROAD understanding of temperature patterns Isotherm: line connecting points of equal temperature

Global Temperature Patterns Primary controls on global temperature Altitude Temperature decreases with altitude Latitude Fundamental cause of temperature variation Temperature with latitude Land–Water contrasts Continents have higher summer & lower winter temps than oceans Ocean currents Cool currents push isotherms equatorward; warm currents push isotherms poleward Figure 4-29 – average January temperature Figure 4-30 – average July temperature

Global Temperature Patterns Seasonal patterns Latitudinal shift in isotherms from one season to another More pronounced over continents than water and over high latitudes than low latitudes Figure 4-31

Global Temperature Patterns Annual temperature range Difference in average temperature of warmest and coldest months (usually Jan & July) Figure 4-32

Global Warming and the Greenhouse Effect Climate of Earth is becoming warmer, known as global warming Air temp increases when atmospheric gases trap longwave radiation Human-enhanced greenhouse effect Carbon dioxide main culprit Also methane, nitrous oxide, CFC’s Intergovermental Panel on Climate Change Figure 4-33

Global Warming and the Greenhouse Effect Relationship between carbon dioxide and temperature Figure 4-35

Summary Temperature affects both living and nonliving aspects of Earth’s landscape Energy exists in many different forms, but cannot be created or destroyed Temperature is a measure of the amount of kinetic energy in the molecules of a substance Temperature is measured on three primary scales The Sun is the primary source of energy for Earth’s atmosphere Electromagnetic radiation is classified by wavelength The Sun emits three important types of electromagnetic radiation: visible, infrared, and ultraviolet Insolation refers to incoming solar radiation Radiation is the process by which electromagnetic radiation is emitted by an object Radiation can undergo several processes, including absorption, reflection, transmission, and scattering The greenhouse effect makes Earth able to support life

Summary Conduction is the transfer of heat through molecular collision Convection is a vertical transport of heat in a fluid Advection is the horizontal transport of heat Adiabatic cooling and warming processes do not release or absorb heat The global radiation budget describes the latitudinal distribution of temperature Land surfaces heat and cool faster than water surfaces Heat is transferred globally through atmospheric and oceanic circulations The vertical temperature patterns in the atmosphere help describe vertical circulations Global warming is the observed warming of the atmosphere Temperature and carbon dioxide show a close relationship