1 Our Physical Environment Chapter 3 Atmospheric Temperature Liang Liang, UWM Geography Chapter 3 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 Surface and Air Temperature (1/6) 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 Surface and Air Temperature (2/6) 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) Surface and Air Temperature (3/6) Environmental Contrasts: Urban and Rural Temperatures Surface materials influence temperature strongly Transpiration: the process by which plants lose water to the atmosphere by atmosphere by evaporation through leaf pores Evapotranspiration: the combined water flow to the atmosphere by evaporation from soil and transpiration from plants Surface and Air Temperature (4/6) 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 2 Surface and Air Temperature (5/6) High-Mountain Environments ? Reduced air pressure ?reduced oxygen to lungs ? Fewer air molecules ?sun?s rays stronger ? Less CO 2 and water vapor ?reduced greenhouse effect Surface and Air Temperature (6/6) Temperature Inversion: reversal of normal temperature pattern so that air temperature increases with altitude Daily and Annual Cycles of Air Temperature (1/4) The Daily Cycle of Air Temperature ? Insolation varies by season ? Daylength longest at summer solstice ? Daylength shortest at winter solstice ? Net radiation varies daily Piti ft i? Positive after sunr se ? Peaks at noon ? Decreases to negative by sunset ? Air temperature varies daily ? Minimum just after sunrise ? Rises to a peak in mid-afternoon Daily and Annual Cycles of Air Temperature (2/4) 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 rangesggy Daily and Annual Cycles of Air Temperature (3/4) Land and Water Contrasts Inland climates have more temperature extremes than coastal climates: 1. Solar rays heat land surface but are distributedsurface, but di buted deeper in water 2. Water has higher heat capacity than rock and soil 3. Water mixes 4. Water evaporates, removing latent heat Daily and Annual Cycles of Air Temperature (4/4) Annual Net Radiation and Temperature Cycles Annual cycle of daily insolation affects ?net radiation, which affects ?monthly mean air temperature 3 World Patterns of Air Temperature (1/4) 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 World Patterns of Air Temperature (2/4) 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. Maritime continenta contr st 3. Elevation World Patterns of Air Temperature (3/4) 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 World Patterns of Air Temperature (4/4) World Air Temperature Patterns for January and July Patterns to note: ? Highlands are colder than surrounding lowlands l? Temperatures in equatoria 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 Temperature Structure of the Atmosphere (1/3) Temperature decreases with altitude in the troposphere, then increases above the troposphere Lapse Rate: rate at which air temperature drops with increasing altitude Troposphere: lowest layer of the atmosphere, in which temperature falls steadily with increasing altitude Temperature Structure of the Atmosphere (2/3) Troposphere ? Lowest layer of atmosphere ? Temperature normally decreases with increasing elevation ? Thickest over equator, thinner q, 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 4 Temperature Structure of the Atmosphere (3/3) Stratosphere and Upper Layers Stratosphere: layer of atmosphere directly above the troposphere; here temperature slowly increases with height ?Strong winds, little water vapor or dustg, ?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 Global Warming and the Greenhouse Effect (1/7) 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 (CO ) dio ide (CO 2 ? Methane (CH 4 ) ? Chlorofluorocarbons (CFC?s) ? Tropospheric ozone (O 3 ) ? Nitrous oxide (N 2 O) Global Warming and the Greenhouse Effect (2/7) Greenhouse Gases: ? Carbon dioxide (CO 2 ) ?Fossil fuel burning, forest destruction ? Methane (CH 4 ) ?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 (O 3 ) ?Motor vehicles ? Nitrous oxide (N 2 O) ?Motor vehicles, nitrogen fertilizer ? Some pollutants have a cooling effect ? Some factors are natural Global Warming and the Greenhouse Effect (3/7) The Temperature Record ? Net warming effect of 1.6 W/m 2 ? Direct records show increase ?Variability ?Influence of volcanic activity of olcanic activit Global Warming and the Greenhouse Effect (4/7) The Temperature Record Reconstructing temperature records: ?Thermometers ?Historical data ?Tree rings ?Coral growth ?Ice cores Global Warming and the Greenhouse Effect (5/7) Future Scenarios ? 2005 warmest year recorded since mid-19 th century ? 2005, 1998, 2002, 2003,2006 five warmest years since 1400 ? Earth?s temperature up: 06ºC(11º F) i l 30?0.6º C (1. n ast 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 5 Global Warming and the Greenhouse Effect (6/7) 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 regions wetter, some drier ?Agricultural patterns shift ?Human populations displaced ?Natural ecosystems displaced ?Arctic thawing ?More variable, extreme climate Global Warming and the Greenhouse Effect (7/7) 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 A Recent Episode Northwest Passage and Northern Sea Route (Northeast Sea Route) both opened early this month. Das Eismeer (The Sea of Ice), 1823?1824 Caspar David Friedrich lliang Microsoft PowerPoint - Geog120_Lec03_Atmos_Temperature.ppt [Compatibility Mode]
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