1 / 30

Lesson 01 Atmospheric Structure

Lesson 01 Atmospheric Structure. Composition, Extent & Vertical Division. Composition. By Volume Nitrogen (N 2 ) 78% Oxygen (O 2 ) 21% Others (1%) Carbon Dioxide (CO 2 ) 0.035% Ozone + Others(Neon, Xenon etc) Water Vapour (variable from 0 - 4% locally). Composition con’t.

terrybrady
Télécharger la présentation

Lesson 01 Atmospheric Structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lesson 01Atmospheric Structure • Composition, Extent & Vertical Division

  2. Composition • By Volume • Nitrogen (N2) 78% • Oxygen (O2) 21% • Others (1%) • Carbon Dioxide (CO2) 0.035% • Ozone + Others(Neon, Xenon etc) • Water Vapour (variable from 0 - 4% locally)

  3. Composition con’t • Analysis reveals no variation in its composition up to at least 60km • except for increasing concentrations of Ozone in the upper Stratosphere. • At higher altitudes, the force of gravity being less causes the proportions to change.

  4. Composition con’t • None of these gases changes its state within the normal temperature range of the atmosphere so dry air remains invisible. • Only water vapour changes its state • water  gas solid

  5. The water cycle, illustrating evaporation, condensation & precipitation

  6. The 3 M’s:- • Moisture • Mass • Movement

  7. Properties of the Earth’s Atmosphere • The earth’s atmosphere varies both vertically and horizontally in terms of: - Pressure - Temperature - Density - Humidity

  8. Properties of the Earth’s Atmosphere, contd. • The atmosphere is also a poor conductor of heat and being a gas is extremely fluid and only supports life in the lower levels. Fifty percent of the atmosphere is below the 500mb pressure level (about 18,000 feet).

  9. Vertical Division • The atmosphere extends to about 1000 km above the earth’s surface and • consists of several layers, each with its own properties. • The layers are defined by the temperature profile as shown in the following diagram..

  10. Vertical Division Ionosphere

  11. Troposphere • Layer in contact with surface • Contains 80% of atmosphere • Temperature decreases with height • Until Tropopause reached • Zone of vertical mixing by convection and turbulence • Contains most of water vapour • Zone of clouds and weather • Heated from below

  12. Tropopause • Indicated by marked change in lapse rate • Upper limit of cloud and weather • Lowest tropospheric temperatures at this level • Strongest winds aloft just below it • Height varies according to season and latitude • H2O decreases, O3 increases

  13. Typical Average Tropopause Heights and Temperatures

  14. Variation in Height of Tropopause • The thickness of the Troposphere will vary according to temperature. • Lower when the air is cold (i.e. polar latitudes) • Higher when air is warm (i.e. equatorial latitudes) • Height therefore depends on season and latitude • Coldest tropopause temperatures over the equator • Breaks in tropopause caused by jet streams

  15. Variation of Surface Pressure with Height of Tropopause • High tropopause • high air column • high surface pressure • more prevalent in summer • near equator • Low tropopause • low air column • low surface pressure • more prevalent in winter • near polar latitudes

  16. Height/temperature graph for tropopause JA, JB, JC = Jetstreams

  17. Layered structure defined by the temperature profile (ELR) through the atmosphere. (Radio sounding)

  18. Radio Sonde

  19. Stratosphere • Temperature increases with height to about 50 km. • Contains warm Ozone region in upper levels at 40-50 km. • Weather does not penetrate but some severe CB’s may penetrate several 1000’s of feet. • Nacreous clouds form at about 20-30 km

  20. Nacreous Clouds

  21. Stratopause • Marks upper limit (50 km), of the stratosphere. • Maximum temperature just below freezing.

  22. Mesosphere • Region of decreasing temperature • Noctilucent clouds form at approximately 80 - 85 km. • Usually visible in summer in Northern sky near midnight.

  23. Noctilucent Cloud North Ayrshire Scotland 1988 July 02-03 00005 UTC

  24. Mesopause • Marks the upper limit of the Mesosphere. • Height approximately 80-90 km. • Temperatures between -120°C (summer) & -50°C (winter) at high latitudes

  25. Thermosphere • Zone of increasing temperature • Upper limit undefined. • Merges into the Exosphere/Ionosphere.

  26. 90% of Ozone found here. Absorbs harmful Ultra Violet (UV) radiation. UV Radiation causes skin cancers. destroys DNA molecules. Ozone filters in aircraft Strongly absorbs IR earth radiation Absorbed energy re-radiated back to earth Helps maintain the thermal balance in the atmosphere Ozone in the Stratosphere

  27. Ozone Production • Ozone produced by interaction of molecular O2 and UV radiation • O2 + UV  O + O • O2 + O  O3 • Ozone forms mainly above 25 km but drifts down producing a peak concentration at 25 km.

  28. Ozone Destruction • Ozone is also destroyed by UV radiation. • O3 + UV  O2 + O • O3 + O  2O2 • Ozone is also destroyed by the collision between two ozone molecules. • O3 + O3  3O2

  29. Ozone Balance • Ozone between 25 and 35 km is maintained by a delicate natural balance • Ozone can be reduced by natural events e.g. solar flares and cosmic rays. • Pollutants such as fluorocarbons also destroy ozone.

More Related