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Metr 100 Section 1

Metr 100 Section 1. Wednesday (9/2/09) Announcements: Reading assignment: Chapters 1 & 2, Ahrens: Essentials of Meteorology. A look at the GOES East satellite today (hurricane discussion) Temperature profiles of the atmosphere

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Metr 100 Section 1

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  1. Metr 100 Section 1 • Wednesday (9/2/09) • Announcements: • Reading assignment: Chapters 1 & 2, Ahrens: Essentials of Meteorology. • A look at the GOES East satellite today (hurricane discussion) • Temperature profiles of the atmosphere • Why does the temperature decrease in troposphere and increase in stratosphere? • Pressure and density profile of the atmosphere • Atmospheric composition (partial pressures) • A look at a recent soundings (uwyo)

  2. Hurricane Jimena

  3. National Hurricane Center Website: http://www.nhc.noaa.gov

  4. Oklahoma Weather Lab GOES-W Full View Infrared http://hoot.metr.ou.edu/satellite/GOES-W/full/1B

  5. Definition of temperature Temperature of gases is a measure of the average kinetic energy (energy of motion) of the molecules of the gas. Kinetic energy is proportional to the mass of the molecules times the square of their velocity Expressed in units of degrees Celsius (°C) , degrees Kelvin (°K = °C+273) or (in the US only) degrees Fahrenheit (°F)

  6. Definition of air pressure The force per unit area exerted by air molecules (nitrogen, oxygen, argon, water vapor, etc.) on any surface (the ground, your face, your inner ear, etc.) Expressed in units of millibars (mb), or hectoPascals (hPa) old: inches-Hg What is the unit of pressure we use in the US to check our tire inflation? Pounds/square inch {over atmosphere}

  7. Definition of Density The ratio of the mass of a substance to the volume occupied by it Expressed in units of kilograms per cubic meter

  8. The vertical temperature distribution of the atmosphere

  9. Graph of pressure vs. height

  10. How air density changes with height

  11. Dalton’s Law of Partial Pressures The total pressure exerted by a mixture of gases which do not interact chemically is equal to the sum of the partial pressures of the gases. The partial pressure of a gas is the pressure it would exert at the same temperature as the mixture if it alone occupied the volume that the mixture occupies.

  12. Composition of the Atmosphere • Nitrogen 78% of molecules • Oxygen, 21% of molecules • Argon, ~ 1% of molecules Dry Air • Water vapor concentrations are variable, up to 4% of total Total cannot be more than 100%; e.g. If water vapor is present, reduce proportion of dry air, as shown in calculations of molecular weight following

  13. Constituent Molecular Weight Fraction Product Nitrogen (N2) 28 .78 21.84 Oxygen (O2) 32 .21 6.72 Argon (A) 40 .01 0.40 Sum 1.00 28.96 The average molecular weight of dry air ≈ 29 Composition of dry air

  14. Constituent Molecular Weight Fraction Product Nitrogen (N2) 28 .78 x .96 20.97 Oxygen (O2) 32 .21 x .96 6.45 Water Vapor (H2O) 18 .04 0.72 Argon (A) 40 .01 x .960.38 Sum 1.00 28.52 The molecular weight of moist air is less than that for dry air 28.52 for 4% water vapor vs 28.96. Composition of very moist air (4%)

  15. Radiosonde soundings from a variety of latitudes. P(mb) vs T(°C) Left trace is Dew Point Temperature (ignore) Right trace is Temperature Green lines are adiabats (neutral buoyancy) Pt. Barrow, AK 71.3°N Vandenberg AFB, CA 34.75°N Canal Zone 10.0°N

  16. Pressure, Height,&Temperatureof Tropopause Station Latitude P(mb) Ht(km) T(°C) T250 Pt.Barrow 71.3 230 11 -56 -52 Vandenberg 34.75 150 14 -65 -48 Canal Zone 10.0 130 15 -77 -42

  17. Local (OAK) 8/31 12Z sounding Balloon broke at 150 mb Display to 700 mb Note temperature inversion and rapid drop in moisture (top of fog layer) Conditions conducive to refraction of VHF/UHF radio waves Note lapse rate < adiabatic--> stable

  18. University of Wyoming Web Site http://weather.uwyo.edu

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