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Adiabatic Processes

Adiabatic Processes. Created By: Mr. Kreeger. Homework and Page References. Textbook-Page 484, Review Book-Page 576 HW #1- Explain why there is a difference between the dry adiabatic lapse rate and the moist adiabatic lapse rate. Explain the conditions responsible for Absolute stability

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Adiabatic Processes

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  1. Adiabatic Processes Created By: Mr. Kreeger

  2. Homework and Page References • Textbook-Page 484, Review Book-Page 576 • HW #1- Explain why there is a difference between the dry adiabatic lapse rate and the moist adiabatic lapse rate. • Explain the conditions responsible for • Absolute stability • Absolute instability • Conditional instability

  3. Table of Contents • Adiabatic changes in temperature • Rising and Subsiding air • Dry air • Moist air • Types of stability • Absolute stability • Absolute instability • Conditional instability • Lapse Rate

  4. 1. Adiabatic changes in temperature • Adiabatic temp change is any change in temp of a system with out any heat being added or removed from that system. • Letting air out of tire-Gas expands temp goes down • Filling tire with air-Gas compressed and heated

  5. Rising and Subsiding Air High P 1. RISING AIR EXPANDS AND COOLS Lower P High P Higher P Lower P Lower P 2. SUBSIDING AIR IS COMPRESSED AND WARMS Low P Higher P (surface)

  6. 1b. Dry Air • When dry air rises or descends, it’s temp changes adiabatically at a rate of 10C per km. (Dry adiabatic Lapse Rate)-DALR

  7. 1c. Moist Air • When moist air rises and cools to dew point condensation occurs and clouds form. • Until clouds form parcel follows DALR(10C/km) • Because latent heat is released during condensation, moist air cools at a slower rate 6C/km(moist adiabatic lapse rate) MALR

  8. Diagram showing what occurs to air as it moves over a mountain

  9. Moistadiabatic Rate (-6°C/km) Dryadiabatic Rate (-10°C/km) Dry and Moist Adiabatic Lapse Rate • The DALR is steeper than the MALR • When dewpoint and temp not equal parcel follows DALR • When dewpoint and temp are equal parcel follows MALR

  10. Types of stability • Distinctions • Environmental lapse rate- Observed temp change with height, measured • DALR, MALR- the rates at which a unsaturated / saturated parcel of air is expected to cool as it rises in the atmosphere

  11. Absolute Stability • When Environmental lapse rate is less than the moist adiabatic lapse rate • Rising parcel always cooler than surrounding air, has tendency to fall back to ground

  12. Absolute Instability • Environmental lapse rate is greater than dry adiabatic lapse rate. • Ascending air always less dense than surrounding air, wants to continue to rise

  13. Conditional Instability • When environmental lapse rate is between DALR and MALR. • Unsaturated parcel is stable • Saturated parcel is unstable

  14. In General

  15. 2. Lapse Rate • Parcel of air rises cools capacity to hold water vapor decreases RH increases. • Moist air rises and condenses, releasing latent heat (540cal/gm)slows rate of cooling. Keeps rising air low in density and warmer than surrounding air sustains rising motion • Tops of T-storms can penetrate stratosphere

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