GEO 203 Notes – 10/14/10 (Lecture #9, Part 2: Atmospheric Stability)[Review] Atmosphere is absolutely stable when environmental lapse rate < moist adiabatic lapse rateDry (unsaturated) adiabatic lapse rate Gd: 10 C per 1000mMoist (saturated) adiabatic lapse rate Gs: 6 C per 1000mWarm object density < cold object densityAtmosphere is absolutely unstable when environmental lapse rate > dry adiabatic lapse rateUsually short-lived; usually results from surface heating and is confined to shallow layer near surfaceVertical mixing can eliminate itMade unstable by cooling aloft and warming belowDue to cold air advection or cloud radiational coolingWarming of surface air due to solar heating, warm air advection, air moving over warm surface (warm body of water/lake-effect snow)Atmosphere is conditionally unstable when environmental lapse rate is between dry and moist adiabatic lapse rates (between 6 and 10 C per 1000m)Atmosphere is stable with respect to unsaturated air, but is unstable with respect to saturated airAtmosphere is most unstable in afternoon, summer; most stable at night, winter(Lecture #10: Clouds and Cloud Development)Howard Cloud Classification System (1803)Uses Latin words to describe height and appearanceFactors described: Height: low, mid, high, verticalAppearance: shape, density, colorStratus (‘layer’): sheet-like cloudsCumulus (‘heap’): puffy cloudsCirrus (‘curl of hair’): wispy cloudsNimbus (‘violent rain’): rain cloudsEverything is lower in polar region (i.e. tropopause, cloud base)Low clouds: Cloud base < 2,000ftStratus (St)Stratocumulus (Sc)Nimbostratus (Ns)Middle clouds: Cloud base = 2,000-6,000ftAltostratus (As), Altocumulus (Ac)High clouds: Cloud base > 6,000ftCirrus (Ci), Cirrostratus (Cs), Cirrocumulus (Cc)Clouds with vertical developmentCumulus (Cu), Cumulonimbus (Cb)Cirrus: High clouds that are white, thin, wispy, and comprised mostly of ice crystalsIndicates that weather will change soon Cirrocumulus: High clouds that are rounded white puffs (possibly in rows), cover small portion of sky, and are less common than cirrusMackerel skyCirrostratus: High clouds that thinly cover entire sky with ice crystals; light passing through may form a haloAltocumulus: Middle clouds that are puffy masses of white with gray edges with blue sky between patchesAltostratus: Middle clouds that cover entire sky; may create dimly visible/watery sun and diminish formation of shadowsNimbostratus: Low clouds with precipitation that reaches ground; shredded parts of these clouds called stratus fractus or scudSteady precipitationStratocumulus: Low clouds with rounded patches that range from light to dark gray with blue sky between patchesStratus: Low clouds that resemble fog but do not reach ground; can generate light mist or drizzleCumulus: Clouds that take variety of shapes and look like floating cotton, separated by sinking air and blue skyCumulus congestus: Clouds with vertical development that become larger in height; tops have ragged shape like cauliflowerIndicates that rain is comingCumulonimbus: Vertically developed clouds with heavy precipitation; often assoc. with storms; flattenedanvil shape, indicating that the cloud top is reaching tropopauseClouds cannot go above tropopause because of the lapse rate; temperature increases with height (stable) in stratosphere, so air parcel cannot rise and cloud cannot formSTUDY DESCRIPTION AND HEIGHT CLASSIFICATIONUnusual cloudsLenticular: lens shape, forms crest of waveBanner: lenticular cloud that forms downwind of mountain peak and is regularly replenished by condensing water vaporPileus (cap): cap on top of sprouting cumulusMammatus: rounded masses that hang beneath clouds (usually under thunderstorm)Contrail: Cirrus-like trail behind jet aircraftSky conditions: cloud coverage divided into eighth and each amount associated with term such as scattered condition (?)Clear: 0-5%Few: 5-25%Scattered: 25-50%Broken: 50-87%Overcast: 87-100%Ceilometer used at airports to determine height from cloudsHeight can be determined via infrared satellite (bright = height)STUDY: Focus on notes, chapters in book that correspond to lessonsQUIZ TUESDAY ON STABILITY, CLOUDS, DEW POINT,