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atms 305 atmospheric thermodynamics and statics

Today's lecture topics:The Concept of Static Stability (W

JasminFlorian
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atms 305 atmospheric thermodynamics and statics

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    1. Today’s lecture objectives: The Concept of Static Stability (W&H 2.7) Now that we know how to deal with phase changes inside the air (Polly) parcel, how does the temperature inside the air (Polly) parcel compare to the environmental air? ATMS 305 – Atmospheric Thermodynamics and Statics

    2. Today’s lecture topics: The Concept of Static Stability (W&H 2.7) What is meant by stability? Unsaturated air Archimedes’ Principle and buoyancy Saturated air Conditional and convective instability ATMS 305 – The Concept of Static Stability

    3. Meteorological Stability The ability of the air to return to its origin after displacement

    4. Stability Depends on the thermal structure of the atmosphere

    5. Stability Can be classified into 3 categories Stable Neutral Unstable

    6. Stable Returns to original position after displacement

    7. Neutral Remains in new position after being displaced

    8. Unstable Moves farther away from its original position

    9. Stability How is air displaced? Two methods 1.) Forced Ascent 2.) Auto-Convective Ascent

    10. Forced Ascent Some mechanism forces air aloft Usually synoptic scale feature

    11. Forced Ascent Type of clouds Depends on stability

    12. Auto-Convective Ascent Air becomes buoyant by contact with warm ground Usually microscale or mesoscale

    13. Auto-Convective Ascent Type of Clouds Cumulus

    14. Stability As parcel rises 1.) Parcel Temperature Changes Unsaturated? Dry Adiabatic Lapse Rate

    15. Dry Adiabatic Lapse Rate

    16. Archimedes’ Principle The buoyant force exerted by a fluid on an object in the fluid is equal in magnitude to the weight of fluid displaced by the object.

    17. Archimedes’ Principle ‘Square’ bubble in a tank of water

    18. Archimedes’ Principle Water pressure in tank increases with depth

    19. Archimedes’ Principle Water is in hydrostatic equlibrium

    20. Archimedes’ Principle Force on bottom of ‘bubble’

    21. Archimedes’ Principle Force on top of ‘bubble’

    22. Archimedes’ Principle Buoyancy Force

    23. Archimedes’ Principle Horizontal Pressure Differences Balance

    24. Archimedes’ Principle Pressure Difference Between Top & Bottom

    25. Archimedes’ Principle Combine Equations

    26. Archimedes’ Principle Cartoon here??

    27. Buoyancy Similar to parcel of air in atmosphere At Equilibrium Density of Parcel Same as Density of Environment

    28. Buoyancy Density Difference Results in Net Buoyancy Force

    29. Buoyancy Density Difference Results in Net Buoyancy Force

    30. Buoyancy Net Buoyancy Force

    31. A parcel of unsaturated air originally located at level O Environment A T-storm possible or not? ATMS 305 – The Concept of Static Stability

    32. A parcel of unsaturated air originally located at level O Environment B T-storm possible or not? ATMS 305 – The Concept of Static Stability

    33. Stability As parcel rises 1.) Parcel Temperature Changes Saturated? Pseudoadiabatic Lapse Rate

    34. Pseudo-Adiabatic Lapse Rate Varies with dws/dT

    35. If a parcel of air is saturated: Static stability Static instability Static neutrality ATMS 305 – The Concept of Static Stability

    36. ATMS 305 – The Concept of Static Stability Conditional instability Level of free convection Altitude above which the parcel develops a positive buoyancy which carries it upward even in the absence of further lifting

    37. ATMS 305 – The Concept of Static Stability Conditional instability If the environmental lapse rate is between the dry and saturated adiabatic lapse rates, there is the possibility of gravitational instability if vertical motions are large enough to lift air parcels beyond their level of free convection

    38. Convective (or potential) instability An air parcel at “A” will reach its lifting condensation level almost immediately, and beyond that point it will cool moist adiabatically. An air parcel at “B” will cool dry adiabatically through a deep layer before it reaches its LCL. As the inversion layer is lifted, the top part cools much more rapidly than the bottom part and the lapse rate quickly becomes destabilized ATMS 305 – The Concept of Static Stability

    39. Conditional and convective instability Throughout the tropics, the lapse rate is conditionally unstable up to 15 km; convectively unstable up to 6 km Why doesn’t deep convection break out everywhere in the tropics? ATMS 305 – The Concept of Static Stability

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