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Weather and Climate: Elements, Composition, Structure, and Controls

This informative text provides an overview of weather and climate, discussing the elements, composition, structure, and controls of the atmosphere. It also explores temperature measurement, temperature controls, and the global distribution of temperature.

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Weather and Climate: Elements, Composition, Structure, and Controls

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  1. Weather

  2. Weather Weather is over a short period of time Constantly changing Climate Climate is over a long period of time Generalized composite of weather Weather and climate

  3. Weather and climate • Elements of weather and climate • Temperature • Humidity • Cloudiness • Precipitation • Air Pressure • Winds speed and direction

  4. The Atmosphere Composition Structure Heating

  5. Composition of the atmosphere • Gases • Nitrogen (N) – 78% • Oxygen (O2) – 21% • Argon and other gases • Carbon dioxide (CO2) – 0.036%

  6. Composition of the atmosphere • Variable components of air • Water vapor • Aerosols • Ozone

  7. Structure of the atmosphere • Pressure changes • Pressure is the weight of the air above • Average sea level pressure • Pressure decreases with altitude

  8. Structure of the atmosphere • Atmospheric layers based on temperature • Troposphere • Stratosphere • Mesosphere • Thermosphere

  9. Earth-Sun relations • Earth motions • Rotates on its axis • Revolves around the Sun

  10. Earth-Sun relations • Seasons • Caused by Earth's changing orientation to the Sun • Axis is inclined 23½º • Axis is always pointed in the same direction

  11. Earth-Sun Relations

  12. Atmospheric heating • Heat is always transferred from warmer to cooler objects

  13. Atmospheric heating • Incoming solar radiation • Reflection – albedo (percent reflected) • Scattering • Absorption • Most visible radiation reaches the surface

  14. Atmospheric heating • Outgoing Radiation • Earth re-radiates radiation (terrestrial radiation) at the longer wavelengths • Terrestrial radiation is absorbed by • Carbon dioxide and • Water vapor in the atmosphere • Lower atmosphere is heated from Earth's surface • The greenhouse effect

  15. Atmospheric Energy Balance

  16. Temperature Measurement Controls World Distribution

  17. Temperature measurement • Daily maximum and minimum • Other measurements • Daily mean temperature • Daily range • Monthly mean • Annual mean • Annual temperature range

  18. Mean monthly temperatures for Vancouver, British Columbia and Winnipeg, Manitoba Mean monthly temperatures for Eureka, California and New York City

  19. Temperature measurement • Human perception of temperature • Important factors are • Air temperature • Relative humidity • Wind speed • Sunshine

  20. Controls of temperature • Temperature variations • Receipt of solar radiation is the most important control • Other important controls • Differential heating of land and water • Land heats more rapidly than water • Land gets hotter than water • Land cools faster than water • Land gets cooler than water

  21. Controls of temperature • Other important controls • Altitude • Geographic position • Cloud cover • Albedo

  22. Clouds reduce the daily temperature range

  23. World distribution of temperature • Global temperature patterns • Temperature decreases poleward from the tropics • Isotherms exhibit a latitudinal shift with the seasons • Warmest and coldest temperatures occur over land

  24. World distribution of temperature • Global temperature patterns • Isotherms show ocean currents • Annual temperature range • Small near equator • Increases with an increase in latitude • Greatest over continental locations

  25. World mean sea-level temperatures in January

  26. World mean sea-level temperatures in July

  27. Formation of Weather Atmospheric Circulation Wind Patterns Air Masses Fronts Cyclones & Anticyclones Cloud Formation

  28. Air at high elevations is: Cooler Expands Water vapor tends to condense Air at sea level is: Warmer More compressed Can hold more water vapor Solar Heating and Atmospheric Circulation

  29. Air Circulation & Convection Currents

  30. Coriolis Force

  31. Atmospheric Circulation & Convection Cells

  32. Wind • Horizontal movement of air • Out of areas of high pressure • Into areas of low pressure • Controls of wind • Pressure gradient force • Isobars – lines of equal air pressure • Pressure gradient – pressure change over distance

  33. Wind Pattern Development

  34. General atmospheric circulation • Idealized global circulation • Equatorial low pressure zone • Rising air • Abundant precipitation

  35. General atmospheric circulation • Idealized global circulation • Subtropical high pressure zone • Subsiding, stable, dry air • Location of great deserts • Air traveling equatorward from the subtropical high produces the trade winds • Air traveling poleward from the subtropical high produces the westerly winds

  36. General atmospheric circulation • Idealized global circulation • Subpolar low pressure zone • Warm and cool winds interact • Polar front – an area of storms

  37. General atmospheric circulation • Idealized global circulation • Polar high pressure zone • Cold, subsiding air • Air spreads equatorward and produces polar easterly winds • Polar easterlies collide with the westerlies along the polar front

  38. Local winds • Produced from temperature differences • Small scale winds • Types • Land and sea breezes • Mountain and valley breezes • Chinook and Santa Ana winds

  39. Illustration of a sea breeze and a land breeze

  40. The Santa Ana Winds

  41. Air masses are classified on the basis of their source region

  42. Fronts • Types of fronts • Warm front • Warm air replaces cooler air • Shown on a map by a line with semicircles • Small slope (1:200) • Clouds become lower as the front nears • Slow rate of advance • Light-to-moderate precipitation

  43. Fronts • Types of fronts • Cold front • Cold air replaces warm air • Shown on a map by a line with triangles • Twice as steep (1:100) as warm fronts • Advances faster than a warm front • Associated weather is more violent than a warm front

  44. Cold Fronts and Warm Fronts

  45. Rotating Air Bodies • Bends in the polar jet create troughs and ridges • Forms cyclones and anticyclones

  46. Low Pressure Zone Formation Warm air rises Creates a low pressure zone At the Earth’s surface, air “feeds” the low pressure zone, moves counterclockwise High Pressure Zone Formation Cool air sinks Creates a high pressure zone At the Earth’s surface, winds blow clockwise Rotating Air Bodies

  47. Cyclones and Anticyclones

  48. Changes of state of water • Three states of matter • Solid • Liquid • Gas • To change state, heat must be • Absorbed, or • Released

  49. Changes of state of water

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