1 / 28

LISTSERV

LISTSERV. You can subscribe by sending an email to listserv@listserv.arizona.edu with the following as the only line in the body of the message. subscribe nats101s34 Firstname Lastname Substitute your first name for Firstname Substitute your last name for Lastname.

chauncey
Download Presentation

LISTSERV

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. LISTSERV You can subscribe by sending an email to listserv@listserv.arizona.edu with the following as the only line in the body of the message. subscribe nats101s34 Firstname Lastname Substitute your first name for FirstnameSubstitute your last name for Lastname

  2. NATS 101 - 34Lecture 2Hurricane Dean & 2006 climate anomaliesAtmosphericCompositionDensity, Pressure & Temperature

  3. http://www.ncdc.noaa.gov/oa/climate/research/2006/ann/ann06.htmlhttp://www.ncdc.noaa.gov/oa/climate/research/2006/ann/ann06.html

  4. Atmospheric CompositionPermanent Gases • N2 and O2 are most abundant gases • Percentages hold constant up to 80 km • Ar, Ne, He, and Xe are chemically inert • N2 and O2 are chemically active, removed & returned Ahrens, Table 1.1, 4th Ed.

  5. Atmospheric CompositionImportant Trace Gases Ahrens, Table 1.1, 3rd ed. Which of these is now wrong even in the 4th edition of Ahrens?

  6. CO2 Trend “Keeling Curve” Some gases vary by season and over many years. The CO2 trend is the cause for concern about global warming. CO2 increases in northern spring, decreases in northern fall See http://earthguide.ucsd.edu/globalchange/keeling_curve/01.html

  7. H2O Vapor VariabilityPrecipitable Water (mm) Some gases can vary spatially and daily

  8. Two Important Concepts Let’s introduce two new concepts... Density Pressure

  9. What is Density? Density () = Mass (M) per unit Volume (V)  = M/V  = Greek letter “rho” Typical Units: kg/m3, gm/cm3 Mass = # molecules (mole)  molecular mass (gm/mole) Avogadro number (6.023x1023 molecules/mole)

  10. a b Density Change Density () changes by altering either a) # molecules in a constant volume b) volume occupied by the same # molecules

  11. What is Pressure? Pressure (p) = Force (F) per unit Area (A) Typical Units: pounds per square inch (psi), millibars (mb), inches Hg Average pressure at sea-level: 14.7 psi 1013 mb 29.92 in. Hg

  12. Pressure Can be thought of as weight of air above you. (Note that pressure acts in all directions!) So as elevation increases, pressure decreases. Top Higher elevation Less air above Lower pressure Lower elevation More air above Higher pressure Bottom

  13. Density and Pressure Variation Key Points • Both decrease rapidly with height • Air is compressible, i.e. its density varies Ahrens, Fig. 1.5

  14. 10 kg 10 kg 10 kg 10 kg 10 kg 10 kg Why rapid change with height? Consider a spring with 10 kg bricks on top of it The spring compresses a little more with each addition of a brick. The spring is compressible.

  15. Why rapid change with height? Now consider several 10 kg springs piled on top of each other. Topmost spring compresses the least! Bottom spring compresses the most! The total mass above you decreases rapidly w/height.  mass  mass  mass  mass

  16. Why rapid change with height? Finally, consider piled-up parcels of air, each with the same # molecules. The bottom parcel is squished the most. Its density is the highest. Density decreases most rapidly at bottom.

  17. Why rapid change with height? Each parcel has the same mass (i.e. same number of molecules), so the height of a parcel represents the same change in pressure p. Thus,pressure must decrease most rapidly near the bottom. p p p p

  18. Top Bottom A Thinning Atmosphere Lower density, Gradual drop Higher density Rapid decrease NASA photo gallery

  19. Pressure Decreases Exponentially with Height Logarithmic Decrease • For each 16 km increase in altitude, pressure drops by factor of 10. 48 km - 1 mb 32 km - 10 mb 16 km - 100 mb 0 km - 1000 mb 1 mb 48 km 10 mb 32 km 100 mb 16 km Ahrens, Fig. 1.5

  20. Water versus Air Pressure variation in water acts more like bricks, close to incompressible, instead of like springs. Top Air: Lower density, Gradual drop Higher density Rapid decrease Top Water: Constant drop Constant drop Bottom Bottom

  21. Equation for Pressure Variation We can Quantify Pressure Change with Height

  22. What is Pressure at 2.8 km?(Summit of Mt. Lemmon) Use Equation for Pressure Change

  23. What is Pressure at Tucson? Use Equation for Pressure Change Let’s get cocky… How about Denver? Z=1,600 m How about Mt. Everest? Z=8,700 m You try these examples at home for practice

  24. inversion isothermal 6.5oC/km Temperature (T) Profile • More complex than pressure or density • Layers based on the Environmental Lapse Rate (ELR), the rate at which temperature decreases with height. Ahrens, Fig. 1.7

  25. Higher Atmosphere Molecular Composition • Homosphere- gases are well mixed. Below 80 km. Emphasis of Course. • Heterosphere- gases separate by molecular weight, with heaviest near bottom. Lighter gases (H, He) escape. Ahrens, Fig. 1.8

  26. Summary • Many gases make up air N2 and O2 account for ~99% Trace gases: CO2,H2O, O3, etc. Some are very important…more later • Pressure and Density Decrease rapidly with height • Temperature Complex vertical structure

  27. Reading Assignment • Ahrens Pages 13-22; Appendix A & C Problems 1.17, 1.18, 1.20 (1.17  Chapter 1, Question 17) Don’t Forget the 4”x6” Index Cards

More Related