Natural Disasters Tenth Edition Chapter 9 External Energy Fuels Weather and Climate Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-1
Weather Versus Climate Weather: short-term processes Thunderstorms, tornadoes, hurricanes, floods, et cetera Climate: long-term processes Ice Ages, droughts, atmosphere changes, ocean circulation shifts, et cetera Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-2
Figure 9.1 The Electromagnetic Spectrum Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-3
TABLE 9.1 Energy Flow to and From Earth Energy Flow ( 10 12 joules per second) Energy Flow (%) Solar Radiation 173,410 99.97 Direct reflection 52,000 Direct conversion to heat 81,000 Evaporation 40,000 Water transport in oceans and atmosphere 370 Photosynthesis 40 Heat Flow from Interior 44.2 0.025 General Heat flow by conduction 43.9 Volcanoes and hot springs 0.3 Tidal Energy 3 0.0017 Source: Data from Hubbert (1971). Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-4
Figure 9.2 Solar Radiation Reaching Earth Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-5
Solar Radiation Received by Earth (1 of 2) Relative amounts reflected, used in hydrologic cycle and converted to heat are different at different latitudes Equatorial belt (38 o N to 38 o S) faces Sun directly, so massive amounts of solar radiation are absorbed Polar regions receive solar radiation at low angle, results in net cooling Excess heat at equator is transferred through mid-latitudes to polar regions Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-6
Solar Radiation Received by Earth (2 of 2) Climatic feedback cycle in polar regions: Receive less solar radiation colder More snow and ice forms higher albedo (reflectivity) More solar radiation reflected, less absorbed High albedos lower Earth s surface temperature Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-7
Figure 9.3 Energy radiated from Earth s surface and energy absorbed from solar radiation Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-8
Outgoing Terrestrial Radiation Greenhouse effect raises Earth s surface temperature Solar radiation reaches Earth at short wavelengths Absorbed solar radiation raises Earth s surface temperature Excess heat is re-radiated at long wavelengths and absorbed by greenhouse gases (water vapor, CO 2, methane) in atmosphere, then radiated back down to Earth s surface warms Earth s climate About 95% of long wavelength re-radiated heat is trapped Examine greenhouse effect on Earth in Chapter 12: Runaway greenhouse effect in early Earth history Human-increased greenhouse effect of 20 th, 21 st centuries Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-9
Figure 9.4 Long Wavelength Radiation to and from Earth Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-10
TABLE 9.2 Common Albedos of Earth Surfaces Percent Clouds thick 50 85 thin 5 50 Snow fresh 70 90 Ice 60 70 Water high Sun angle low Sun angle 5 10 10 50 Ground bare 10 20 Sand 20 50 Grass 15 25 Forest 5 15 Cities 4 18 Source: Data from Smithsonosin Meteological Tables (1966);Peixoto and Qort (1992). Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-11
Figure 9.5 Albedo (reflectance) of Solar Radiation off Ice is 70-90% Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-12
Processes and Disasters Fueled by Sun Sun powers hydrologic cycle and (with gravity) drives agents of erosion Sun heats Earth unequally Equatorial regions receive about 2.4 times more solar energy than polar regions Earth s spin and gravity set up circulation patterns in ocean and atmosphere to even out heat distribution Circulation patterns determine weather and climate Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-13
Figure 9.6 The Hydrologic Cycle Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-14
Water and Heat (1 of 6) Required amount of heat to raise temperature of water (specific heat) is high Convection: transmission of heat in flowing water or air Conduction: direct transmission of heat through contact Beach example: temperature of high heat capacity water changes little from day to night, but hot beach sand (with low heat capacity) becomes cool at night Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-15
Water and Heat (2 of 6) Water vapor in atmosphere: between 0 and 4% by volume Humidity: amount of water vapor in the air Saturation humidity: maximum amount of water an air mass can hold (increases with increasing temperature) Relative humidity: ratio of absolute humidity to saturation humidity If temperature of air mass is lowered without changing absolute humidity, will reach 100% relative humidity because at each lower temperature, a lower saturation humidity applies When relative humidity reaches 100%, excess water vapor condenses to liquid water temperature = dew point Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-16
Water and Heat (3 of 6) Water absorbs, stores and releases huge amounts of energy changing phases between liquid, solid and gas Ice melting to water absorbs 80 calories of heat per gram of water (cal/g): latent heat Liquid vapor absorbs 600 cal/g: latent heat of vaporization Ice vapor absorbs 680 cal/g: latent heat of sublimation Liquid ice releases 80 cal/g: latent heat of fusion Vapor liquid releases 600 cal/g: latent heat of condensation Vapor ice releases 680 cal/g: latent heat of deposition Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-17
Water and Heat (4 of 6) Air: easily compressed, denser and denser closer to Earth s surface Flows from higher to lower pressure, upward in atmosphere, if can overcome pull of gravity add heat As heated air rises, it is under lower pressure so expands Expansion causes adiabatic cooling (temperature decrease without loss of heat energy) Descending air is compressed and undergoes adiabatic warming (temperature increase without gain in heat energy) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-18
Water and Heat (5 of 6) Air undergoes about 10 o C adiabatic cooling per km of rise, 10 o C adiabatic warming per km of descent (dry adiabatic lapse rate) As air cools, can hold less and less water vapor relative humidity increases When relative humidity = 100% (altitude = lifting condensation level), water vapor condenses and latent heat is released, which slows rate of upward cooling to about 5 o C per km of rise (moist adiabatic lapse rate) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-19
Water and Heat (6 of 6) Differential Heating of Land and Water Low heat capacity of rock land heats up and cools down quickly Winter: Land cools down quickly, so cool air sinks toward ground high-pressure region Ocean retains warmth, so warm, moist air rises Cold, dry air from land flows out over ocean Summer: Land heats up quickly, so hot, dry air rises low pressure Ocean warms more slowly, so cool, moist air sinks over ocean Cool, moist air over ocean is drawn into land, warms over land and rises to cool, condense and form rain summer monsoons Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-20
TABLE 9.3 Thermal Properties of Selected Materials Density (gm/cm 3 ) Specific Heat = (cal/gm c) Heat Capacity (cal/cm 3 / c) Air 0.0013 0.24 0.00031 Quartz sand 1.65 0.19 0.31 Granite 2.7 0.19 0.51 Water 1.0 1.0 1.0 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-21
Figure 9.7 Water is a Bipolar Molecule Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-22
Figure 9.8 The Heat Index Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-23
Figure 9.9 Changes of State of Water Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-24
Figure 9.10 Differential Heating of Land and Water Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-25
Figure 9.11 A Global Energy Budget Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-26
Figure 9.12 The Water Planet Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-27
Layering of the Lower Atmosphere Troposphere: Lowest layer of atmosphere 8 km at poles and 18 km at equator Warmer at base, colder above instability as warm air rises and cold air sinks, constant mixing helps lead to weather Tropopause: Top of troposphere Stratosphere: Stable configuration of warmer air above colder air Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-28
Figure 9.13 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-29
Atmospheric Pressure and Winds Air flows along the pressure gradient from areas of high pressure to areas of low pressure Winds are also deflected to the right (Northern Hemisphere) or left (Southern Hemisphere) by the Coriolis effect Friction results in a flow across the isobars at an angle Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-30
Figure 9.15 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-31
Coriolis Effect (1 of 2) Velocity of rotation varies by latitude: 465 m/sec at equator, 0 m/sec at poles Bodies moving to different latitudes follow curved paths Northern Hemisphere: veer to right-hand side Southern Hemisphere: veer to left-hand side Magnitude increases with increasing speed of moving body and with increasing latitude (zero at equator) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-32
Coriolis Effect (2 of 2) Determines paths of ocean currents, large wind systems, hurricanes (not water draining in sinks or toilets) Merry-go-round analogy: Looking down on counter-clockwise spinning merry-goround is analogous to rotation of Earth s Northern Hemisphere viewed from North Pole Outside edge of merry-go-round (equator) spins much faster than center of merry-go-round (North Pole) Person at center tosses ball at person on edge: person on edge has rotated away and ball curves to right Opposite spin and direction for southern hemisphere Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-33
Figure 9.16 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-34
Atmospheric Pressure and Winds: Rotating Air Bodies Northern Hemisphere: Rising warm air creates low pressure area air flows toward low pressure, in counterclockwise direction Sinking cold air creates high pressure area air flows away from high pressure, in clockwise direction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-35
Figure 9.17 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-36
Figure 9.19 Atmosphere transports heat: low latitudes to high latitudes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-37
General Circulation of Atmosphere: Low Latitudes Solar radiation at equator powers circulation of Hadley cells Warm equatorial air rises at Intertropical Convergence Zone (ITCZ), then cools and drops condensed moisture in tropics Cooled air spreads and sinks at 30 o N and 30 o S, warming adiabatically Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-38
Figure 9.20 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-39
General Circulation of Atmosphere: Middle and High Latitudes Hadley cells create bands of high pressure air at 30 o N and 30 o S Air flows away from high pressure zones Cold air flows over land from poles to collide at polar front around 60 o N and 60 o S Hadley, Ferrel and polar cells convergence at ITCZ (rain) and polar front (regional air masses) Global wind pattern modified by continental masses, mountain ranges, seasons, Coriolis effect Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-40
General Circulation of Atmosphere: Air Masses North America: Cold polar air masses, warm tropical air masses Dry air masses form over land, moist air masses form over ocean Dominant air-mass movement direction is west to east Pacific Ocean air masses have more impact than Atlantic Ocean Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-41
Figure 9.21 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-42
General Circulation of Atmosphere: Fronts Sloping surface separating air masses with different temperature and moisture content, can trigger severe weather, violent storms Cold front: cold air mass moves in and under warm air mass, lifting it up (tall clouds, thunderstorms) Warm front: warm air flows up and over cold air mass (widespread clouds) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-43
Fronts: Cold Front Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-44
Fronts: Warm Front Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-45
General Circulation of Atmosphere: Jet Streams Relatively narrow bands of high-velocity (around 200 km/hr) winds flowing from west to east at high altitudes Pressure decreases more slowly moving upward through warm air than through cold air warm air has higher pressure aloft than cold air warm air flows toward cold air (toward poles) Spin of Earth turns poleward air flows to highspeed jet stream winds from the west (Coriolis effect) Subtropical jet: about 30 o N Polar jet: more powerful, about 60 o N, changing path Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-46
Figure 9.25 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-47
Figure 9.24 Polar Front Jet Stream, 24 January 2012 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-48
General Circulation of Atmosphere: Troughs and Ridges Northern Hemisphere: Meanders in jet stream may help to create rotating air bodies Trough of lower pressure (concave northward bend) Forms core of cyclone (counterclockwise flow) Ridge of higher pressure (convex northward bend) Forms core of anticyclone (clockwise flow) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-49
Figure 9.26 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-50
Observed Circulation of the Atmosphere Significant variation of air pressure and wind patterns by hemisphere and season Seasonal changes not so great in Southern Hemisphere with mostly water surface Northern Hemisphere wind and heat flow directions change with seasons Winter has strong high-pressure air masses of cold air over continents Summer has thermal lows over continents, Pacific and Bermuda highs Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-51
Figure 9.27 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-52
General Circulation of the Oceans: Classification Surface and near-surface ocean waters absorb and store huge amounts of solar energy Some solar heat transferred deeper by tides and winds Surface and deep-ocean circulation transfers heat throughout oceans, affects global climate Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-53
General Circulation of the Oceans: Surface Circulation Surface circulation mostly driven by winds Movement of top layer of water drags on lower layer, etc., moving water to depth of about 100 m Wind-driven flow directions are modified by Coriolis effect and deflection off continents Carries heat from low latitudes toward poles Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-54
Surface Circulation of the Oceans North Atlantic Ocean Warm surface water blown westward from Africa into Caribbean Sea and Gulf of Mexico Westward path blocked by continents, forced northward along eastern side of North America, east to Europe (warms Europe) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-55
Figure 9.28 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-56
General Circulation of the Oceans: Deep Ocean Circulation Oceans: layered bodies of water with progressively denser layers going deeper Water density is generally increased by: Lower temperature Increased dissolved salt content Deep-ocean water flow is thermohaline (from heat, salt) flow: overturning circulation Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-57
General Circulation of the Oceans: Density Ocean water has higher density at High latitudes (lower temperature) Arctic and Antarctic (fresh water frozen in sea ice, remaining water made saltier) Warm climates (fresh water evaporated, remaining water made saltier) Densest ocean water forms in northern Atlantic Ocean and Southern Ocean Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-58
Figure 9.29 Global Ocean Circulation Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9-59