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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

Adiabatic Processes

Created By:

Mr. Kreeger


Homework and page references
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


Table of contents
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


1 adiabatic changes in temperature
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


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)


1b dry air
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


1c moist air
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



Dry and moist adiabatic lapse rate

Moist mountainadiabatic

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


Types of stability
Types of stability mountain

  • 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


Absolute stability
Absolute Stability mountain

  • 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


Absolute instability
Absolute Instability mountain

  • Environmental lapse rate is greater than dry adiabatic lapse rate.

  • Ascending air always less dense than surrounding air, wants to continue to rise


Conditional instability
Conditional Instability mountain

  • When environmental lapse rate is between DALR and MALR.

  • Unsaturated parcel is stable

  • Saturated parcel is unstable


In general
In General mountain


2 lapse rate
2. Lapse Rate mountain

  • 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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