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7. Stability and Cloud Development

7. Stability and Cloud Development. 7.1 Atmospheric Stability 7.2 Determining Stability 7.3 Cloud development. 7.1 Atmospheric Stability. 7.2 Determining stability. Upward acceleration of the air parcel. A stable Atmosphere.

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7. Stability and Cloud Development

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  1. 7. Stability and Cloud Development 7.1 Atmospheric Stability 7.2 Determining Stability 7.3 Cloud development

  2. 7.1 Atmospheric Stability

  3. 7.2 Determining stability Upward acceleration of the air parcel

  4. A stable Atmosphere the environmental lapse rate <the moist adiabatic rate : absolutely stable Cirrostratus, altostratus, nimbostratus, stratus

  5. Cooling of the surface air • Nighttime radiational cooling of the surface • An influx of cold surface air brought in by • the wind • Air moving over a cold surface

  6. Subsidence inversion: the atmosphere becomes more stable when an entire layer of air sinks.

  7. An unstable atmosphere the environmental lapse rate >the dry adiabatic rate : absolutely unstable

  8. A conditionally unstable atmosphere The moist adiabatic rate< the environmental lapse rate <the dry adiabatic rate

  9. Causes of instability • The cooling of the air aloft • Clod advection • Clouds emitting infrared radiation • to space • The warming of the surface air • Daytime solar heating of the surface • Warm advection • Air moving over a warm surface

  10. Mixing tends steepen the lapse rate

  11. The lifting of a layer makes it more unstable

  12. Equivalent potential temperature (상당 온위) How temperature varies with pressure under condition of saturated adiabatic ascent or descent? Equivalent potential temperature: the potential temperature of a parcel of air when all the water vapor has condensed so that its saturation mixing ratio is zero. Conserved quantity during both dry and saturated adiabatic processes

  13. Convective instability Sufficient lifting may cause the layer to become conditionally unstable Lower layer -> moist adiabat Upepr layer -> dry adiabat Wikimedia commons

  14. 7.3 Cloud development

  15. Convection and clouds

  16. Level of free convection: the level where the rising air becomes warmer than the surrounding air Condensation level: the elevation where the cloud forms

  17. Determining convective cloud base

  18. Topography and clouds Rain shadow: leeward side of the mountain where precipitation is noticeably less

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