chapter_03.f10.pdf

Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Chapter 3 Air Temperature Visualizing Physical Geography by Alan Strahler and Zeeya Merali Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Chapter Overview Surface and Air Temperature Daily and Annual Cycles of Air Temperature World Patterns of Air Temperature Temperature Structure of the Atmosphere Global Warming and the Greenhouse Effect Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature Surface Temperature When solar radiation strikes the ground: ?Shortwave radiation absorbed by ground surface and warms surface ?Longwave radiation emitted ?Sensible heat flows by conduction from warm objects to cooler objects ?Latent heat transfer: water evaporates, taking away latent heat, or condenses, releasing latent heat ?Convection redistributes heat in a fluid by mixing Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature Temperatures Close to the Ground* ? Temperatures on the ground usually more extreme than temperatures at standard height ? Soil, surface, and air temperatures vary throughout the day Standard height: 1.2 m (4.0 ft) *The atmosphere cools with altitude or distance from the heat source ? Earth. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature Environmental Contrasts: Urban and Rural Temperatures Surface materials influence temperature strongly Transpiration: the process by which plants lose water to the atmosphere by evaporation through leaf pores Evapotranspiration: the combined water flow to the atmosphere by evaporation from soil and transpiration from plants Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature The Urban Heat Island City centers tend to be several degrees warmer than surrounding suburbs and countryside. Urban Heat Island: area at the center of a city that has a higher temperature than surrounding regions Day time Night time A bit about Air Pressure What do you know about air pressure at high elevations? Gravity pulls the molecules to the Earth. There are more molecules near the surface. Therefore there is higher pressure at lower elevations. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature High-Mountain Environments ? Reduced air pressure?reduced oxygen to lungs ? Fewer air molecules?sun?s rays stronger ? Less CO2 and water vapor?reduced greenhouse effect Peru. Latitude 15°S. Same 15 days in July. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Surface and Air Temperature Temperature Inversion: reversal of normal temperature pattern so that air temperature increases with altitude Normal or Average Lapse rate ? 3.5 F ° per 1000? ft or 6.4 C° per 1000 m Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Daily and Annual Cycles of Air Temperature The Daily Cycle of Air Temperature ? Insolation varies by season ? Daylength longest at summer solstice ? Daylength shortest at winter solstice ? Net radiation varies daily ? Positive after sunrise ? Peaks at noon ? Decreases to negative by sunset ? Air temperature varies daily ? Minimum just after sunrise ? Rises to a peak in mid-afternoon Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Daily and Annual Cycles of Air Temperature Land and Water Contrasts Maritime temperatures: Coastal regions have smaller daily and annual temperature ranges Continental temperatures: Inland regions have greater daily and annual temperature ranges One week in the summer. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Daily and Annual Cycles of Air Temperature Land and Water Contrasts Inland climates have more temperature extremes than coastal climates: 1. Solar rays heat land surface, but are distributed deeper in water 2. Water has higher heat capacity than rock and soil 3. Water mixes 4. Water evaporates, removing latent heat Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Daily and Annual Cycles of Air Temperature Annual Net Radiation and Temperature Cycles Annual cycle of daily insolation affects?net radiation, which affects?monthly mean air temperature Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. World Patterns of Air Temperature Air temperature maps use isotherms to show centers of high and low temperatures, and temperature gradients Isotherm: line on a map drawn through all points with the same temperature Temperature gradient: rate of temperature change along a selected line or direction Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. World Patterns of Air Temperature Factors Controlling Air Temperature Patterns Three main factors explaining world isotherm patterns: 1. Latitude affects annual insolation, temperatures, and seasonal temperature variation 2. Maritime-continental contrast 3. Elevation (In the northern Hemisphere, the isotherms, like the birds, ?go south for the winter.? Annual range in C°. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. World Patterns of Air Temperature World Air Temperature Patterns for January and July Patterns to note: ?Large land masses in Arctic and subarctic zones are extremely cold in winter?colder than adjacent oceans ?Ice and snow reflect insolation ?Temperatures decrease from equator to poles ?Areas of permanent ice and snow are always intensely cold ?High elevation ?Snow and ice reflect insolation Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. World Patterns of Air Temperature World Air Temperature Patterns for January and July Patterns to note: ? Highlands are colder than surrounding lowlands ? Temperatures in equatorial regions change little from season to season ? Isotherms make large shifts poleward over continents in summer, while isotherms over oceans shift less ?Continents heat/cool faster than oceans Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Temperature Structure of the Atmosphere Lapse Rate: rate at which air temperature drops with increasing altitudeTroposphere: lowest layer of the atmosphere, in which temperature falls steadily with increasing altitude Temperature decreases with altitude in the troposphere, then increases above the troposphere Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Temperature Structure of the Atmosphere Troposphere ? Lowest layer of atmosphere ? Temperature normally decreases with increasing elevation ? Thickest over equator, thinner toward the poles ? Significant amounts of water vapor ? Contains aerosols ?Water vapor condenses on aerosols ?Aerosols scatter sunlight ? Tropopause: top of troposphere Aerosols: tiny particles present in the atmosphere Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Temperature Structure of the Atmosphere Stratosphere and Upper Layers Stratosphere: layer of atmosphere directly above the troposphere; here temperature slowly increases with height ?Strong winds, little water vapor or dust ?Ozone layer ?Stratopause is top of stratosphere Upper Layers: ?Mesosphere ?Thermosphere Homosphere: region of atmosphere in which gas composition is uniform Heterosphere: Upper atmosphere, gas molecules sorted into layers Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect Factors Influencing climatic Warming and Cooling Earth is getting warmer. Intergovernmental Panel on Climate Change: global warming is ?unequivocal?, very likely caused by human activity Greenhouse Gases: ? Carbon dioxide (CO2) ? Methane (CH4) ? Chlorofluorocarbons (CFC?s) ? Tropospheric ozone (O3) ? Nitrous oxide (N2O) Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect Greenhouse Gases: ? Carbon dioxide (CO2) ?Fossil fuel burning, forest destruction ? Methane (CH4) ?Rice cultivation, farm animal wastes, bacterial decay in sewage and landfills, fossil fuel use, biomass burning, wetlands (natural) ? Chlorofluorocarbons (CFC?s) ?Synthetic compounds ? Tropospheric ozone (O3) ?Motor vehicles ? Nitrous oxide (N2O) ?Motor vehicles, nitrogen fertilizer ? Some pollutants have a cooling effect ? Some factors are natural CO2 at Mauna Loa Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect The Temperature Record ? Net warming effect of 1.6 W/m2 ? Direct records show increase ?Variability ?Influence of volcanic activity Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect The Temperature Record Reconstructing temperature records: ?Thermometers ?Historical data ?Tree rings ?Coral growth ?Ice cores Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect Future Scenarios ? 2005 warmest year recorded since mid-19th century ? 2005, 1998, 2002, 2003,2006 five warmest years since 1400 ? Earth?s temperature up: ?0.6º C (1.1º F) in last 30 years ?0.8º C (1.4º F) in last 100 years ? IPCC projects increase in global temperatures between 1.8º C (3.2º F) and 4.0º C (7.2º F) by 2100 Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect Future Scenarios Potential future effects of greenhouse warming: ?Rise in sea level 28 to 43 cm (11.0 to 16.9 in) by 2100 ?Up to 92 million people displaced ?Spread of insect-borne diseases ?Climate boundaries shift ?Some regions wetter, some drier ?Agricultural patterns shift ?Human populations displaced ?Natural ecosystems displaced ?Arctic thawing ?More variable, extreme climate Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Global Warming and the Greenhouse Effect International efforts to reduce greenhouse emissions: ? 1992 Rio de Janeiro Earth Summit ? 1997 Kyoto Protocol ? 1998 Buenos Aires ? 2005 Montreal Solutions will require use of energy sources that produce power without releasing CO2: ? Solar ? Wind ? Geothermal ? Nuclear Pattie PowerPoint Presentation