Stability of Atmosphere Stable conditions • Air rises due to a number of factors • Expands as it rises: cools as it does so Clouds and Precipitation – Can calculate the new temperature – Use the adiabatic lapse rate: Pressure and Wind • Dry for unsaturated • Wet for saturated – Compare the temperature of the air that has risen to the temperature of the air at that height – Use the environmental lapse rate • Higher density air that has risen is stable (cooler) • Lower density air that has risen is unstable (warmer)
Stability Absolute instability Stability
• Environmental lapse rate • Environmental lapse rate ¾5°C/1000 m ¾12°C/1000 m • Dry adiabatic lapse rate • Dry adiabatic lapse rate ¾10°C/1000 m ¾10°C/1000 m • Rising air is cooler than area it rises into • Rising air becomes warmer than area it • Stable!! rises into • Unstable!! • More unstable upon reaching dew point!
Conditional stability Surface inversion Inversion aloft
• Note the environmental temperature is cool at the surface, increases for some distance, then decreases at greater height • These inversions are stable because the warmer air is buoyant over colder surface
1 LA Basin Inversion Inversion Layer—Los Angeles Cloud Development
• Air cools upon rising • Cools to dew–point temperature • Condensation begins • “Lifting condensation level”
Cloud Shapes Cloud Groups cirrus
• Cirrus—curl (of hair): thin wisps • High clouds—6000 m or more above surface • Stratus—blanket: extensive layers • Middle clouds—2000 m to 6000 m above • Cumulus—pile: puffy masses • Low clouds—less than 2000 m above surface Additional modifier of name • Clouds of vertical development – Present through more than one level • Nimbus = rain – Product of atmospheric instability ¾Cumulonimbus: puffy rain clouds ¾Nimbostratus : layered rain clouds
Cirrocumulus Cirrostratus Altocumulus
2 Altostratus Nimbostratus Cumulus
Cumulonimbus Cloud classification—left Cloud classification—right
Fog—Golden Gate Bridge Fog—Tule Fog Condensation in clouds
3 Bergeron Process of ice-crystal Bergeron notes growth Collision coalescence
Glaze ice Giant hailstone Hail damage
Rime ice Pogonip Precipitation measurement
http://grannysatticquilts.com/pogonip.html
4 http://www.ptguide.com/weather/index.html Precipitation Map of Washington Weather radar display Windfarm in California
Hurricane at Corpus Christi Mercury Barometer Aneroid Barometer
Aneroid Barograph Isobars No Coriolis Effect
5 Coriolis Effect Geostrophic Winds 500 millibar altitude chart
Ridge and trough of 500 mb Upper level wind Surface Wind
Cyclonic circulation—northern Vertical Airflow around Cyclonic and anticyclonic winds hemisphere cyclonic/anticyclonic winds
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