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Meteorology

Meteorology. The study of Earth’s atmosphere. Weather vs. Climate. Weather : Wind, temperature, precipitation, cloud cover and air pressure. Can be localized. Climate : long-term wx conditions over a large area. Classification based upon temp. and precip. Atmosphere. Composition:

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Meteorology

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  1. Meteorology The study of Earth’s atmosphere

  2. Weather vs. Climate • Weather: Wind, temperature, precipitation, cloud cover and air pressure. Can be localized. • Climate:long-term wx conditions over a large area. Classification based upon temp. and precip.

  3. Atmosphere Composition: • 78 % Nitrogen • 21 % Oxygen • .036% Carbon Dioxide* • Rest: water vapor; dust; ozone; argon * Has the most impact, meteorologically speaking

  4. Refer to Atmosphere Layers Hand Out (A)Troposphere: up to ~12km. Where we live, where wx occurs. Temp.↓as altitude↑. Rate of change: 6.5 oC/km. Thinnest layer (B)Stratosphere: ~12km-50km Contains the O3 (Ozone) Layer

  5. Stratosphere cont’d As elevation increases, temperature increases due to the absorption of radiation by the O3 Layer UV rays + O3 O2 + O O3

  6. Ozone Layer and Stratosphere cont’d This rxn in the O3 Layer causes UV rays to get absorbed. If the rxn is disrupted (as in below), then holes in the O3 layer form. This allows more UV rays to reach the earth’s surface, increasing skin cancers, etc. UV rays + O3 O + O2 + CFC’s CFCO + O2 The result: Depleting the Ozone Layer so there is less Ozone to react w/the UV rays, more UV rays get to Earth’s surface

  7. Layers and layers continued • C.)Mesosphere: extends to 80 km. As altitude Temp. Upper part called mesopause. Avg temp. -90oC

  8. Just one more layer………. • D.)Thermosphere: (80-400 km) contains the ionosphere in its lower portion. Temp. increases as altitude increases due to the absorption of short-wave, high-energy solar radiation

  9. Not quite done yet…………. • Auroras occur in the ionosphere. Energetic electrically charged particles (mostly electrons) accelerate along the magnetic field that surrounds the Earth. They collide with gas atoms and solar radiation, causing the atoms to give off light.

  10. Heat Transfer • Conduction: transfer of heat through matter by molecular activity. Energy is transferred through collisions of one molecule to another

  11. Heat Transfer • Convection: the movement of matter due to the differences in density which is caused by differences in temp.

  12. Heat Transfer • Radiation:transfer of heat energy through space via electromagnetic waves. Electromagnetic waves can travel in the absence of matter (mechanical waves, like sound, can not).

  13. Meet ROYGBIV(Not who….what) ROYGBIV stands for the electromagnetic spectrum (light) • R=Red • O=Orange • Y=Yellow • G=Green • B=Blue • I= Indigo • V=Violet When “white” light (from the sun) is separated (like a rainbow), it separates into these colors

  14. Wavelength long short V I S I B L E RedOrange YellowGreenBlueIndigoViolet infrared Ultra-Violet LowFrequency – EnergyHigh

  15. Weather Principles and Vocab……

  16. ! • Pressure= Force/area • Pressure is measured in Pascals (Pa) • 1 Pa = 1 Newton (force)/m2 (area) • AIR PRESSURE is measured in milli bars (mb) • 1 mb = 100 Pa • Standard air pressure at sea level = 1013.2 mb (aka 29.9 inches of mercury)

  17. What is needed for precipitation? • Temp. of pocket of air>Temp. of environment (Tp>Te) This causes: • Vertical transport, which causes Instability.. Need pocket of air to rise in order for it to cool, condense and precipitate • Condensation/Moisture. USUALLY 75% relative humidity

  18. THEREFORE….. • IN GENERAL, precipitation will not occur when a high pressure system is in control. • If the pressure is high, then the air SUBSIDES (sinks)….if it sinks will not get the instability, etc needed for precipitation.

  19. So what do you get w/a high pressure system? • USUALLY…fair weather, light winds • Tp<Te=subsidence/stable condition

  20. What gives “bad” weather/precipitation? • IN GENERAL, a LOW PRESSURE system • Tp>Te, causing the air to rise, get the instability, condensation, etc

  21. Low Pressure System • Pressure is low so the surrounding air pressure, in contrast, is high. • High pressure wants to go to low • That replacing air rises….causes the instability and condensation needed for precip/poor wx

  22. What causes Pressure Differences? Temp. differences Density differences Pressure differences

  23. So……WHAT causes the temp differences??????? • Uneven heating/ cooling of the Earth’s surface. • These cause AIR MASSES that then cause FRONTS/FRONTAL SYSTEMS

  24. Continental Polar cP) Maritime Polar(mP) mP cP Continental Tropical (cT) Page 603 in book Maritime Tropical (mT) mT Air Masses

  25. Maritime Polar (mP) Continental Polar (cP) Continental Tropical(cT) Maritime Tropical (mT) Moist (from off the ocean), cold from the “poles” Dry from off the continent(land), cold from the “poles” Dry from off the land; warm from equator Moist from off the ocean, warm from the equator Air MassesNames and Properties

  26. FRONTS • Warm front • Cold front WARM AIR COLD AIR

  27. Warm Front • Incoming air is warmer (less dense)than air it is “replacing” • Warm “over runs” air it is replacing • Often get cirrus clouds as warm front approaches • Can get precip. Usually not “violent”(ex: showers, drizzle)

  28. Cold Front • Incoming air is colder (more dense) than the air it is replacing • “Replaced” air rises quickly • Get precip that could be violent (thunderstorms, tornadoes)

  29. Stationary Front • Unsettled wx stalls. Usually “drizzley” • Overcast

  30. Occluded Front • Cold front catches up to warm front • Weather can be VERY violent (more than a cold front) thunderstorms, tornadoes

  31. Definitions: • Dewpoint:The temperature at which air becomes totally saturated w/water • Humidity: amount of water vapor in the air • Relative Humidity: air’s water vapor content to its water vapor capacity. Capacity can change w/temp. HOW/WHY? (temp. capacity )

  32. Formula for RHYeah!!! Math in Science Relative Humidity (RH)= Absolute humidity/Capacity X 100=% Ex: at 10oC capacity is 11.0g/cm3 The actual humidity(absolute)might be 5.5g/cm3, so…… 5.5/11 x 100=50% RH

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