# Shared Flashcard Set

## Details

Weather and Climate - Test 2
Weather and Climate - Test 2
56
Geography
09/23/2008

Term
 saturated air
Definition
 when total # of H2O molecules evaporating from body/bodies of water is in equilibrium with condensing-no net loss or gain of liquid molecules**more likely to occur in cool air than in warm**
Term
 condensation nuclei
Definition
 -microscopic bits of dust, smoke, and salt upon whose surfaces condensation of water vapor begins in the atmosphere-in cold air, molecules move more slowly and are more apt to stick to these nuclei-when billions condense onto this nuclei, cloud droplet forms
Term
 humidity and measures of it
Definition
 -refers to any of a number of ways of specifying air's water vapor amount-in hot/humid air... up to 4% volume1)absolute humidity-water vapor density: compares mass of water vapor with volume of air.... g/m^32)specific humidity - compare mass of water vapor with total mass of all air (including vapor).. g/Kg3)mixing humidity- compare mass of water vapor to mass dry air4)actual vapor pressure - total pressure of air with relation to amount of vapor (1% vapor in 1000 millibars equals 10mb of actual vapor pressure)5)saturation vapor pressure - describes how much water vapor is necessary to make the air saturated at any given T6)relative humidity - ratio of amount of water vapor in the air to the max amount of water vapor required for saturation of that particular temperature...given as a percent.. 100%=supersaturated-RH = AVP/SVP.... can be changed by vapor content or T
Term
 dew point (Td)
Definition
 -the temperature TO WHICH air would have to be cooled with no change in air pressure/moisture content for saturation to occur.-this is a good indicator of air's actual water vapor content***high dew point = high H2O vapor content-it is difficult to measure, but easy to calculate if you already have Tw-hydrometeoric (snow/sleet/hail/rain/etc) and atmospheric (clouds/fog) all result because T is cooled to dewpoint-high dew points result in violent storms****when air temp and dew point are equal, air is saturated and RH is 100% (though air may still be considered dry... it is a relative measure)
Term
 Tw
Definition
 -wet-bulb temperature is the lowest T(@ saturation) that can be reached by evaporating water into the air... it is a good way to measure how cool skin can become-when it exceeds skin T... no evap occurs-usually lower than skin temp
Term
 heat index determines...
Definition
 -apparent temp- what air T feels like to person
Term
 hygrometers
Definition
 -instruments used to measure humidity-most common is psychrometer... 2 thermometers... one wet and one dry... wet bulb depression is the difference in temp between the two
Term
 dew
Definition
 -tiny visible specks of water that form when water vapor condenses when ground cools at night-cloudy/windy weather that inhibits rapid cooling near earth often signifies approach of rain-system
Term
 frost
Definition
 -crystals formed be deposition-must reach "frost point"
Term
 haze
Definition
 -layer of particles dispersed through a portion of atmosphere
Term
 fog
Definition
 -cloud resting near the ground-forms either by cooling to below saturation point or evaporationTypes:-radiation fog-advection fog-upslope fog-evaporation fog
Term
Definition
 -(ground fog) - produced by earth's radiational cooling-most common late fall and winter (longer nights)-ideal is a light breeze... small amount of mixing but not blowing away-forms normally in low-lying areas (cold air sinks)-fog usually dissipates by afternoon-radiation causes air to cool below dew point
Term
Definition
 -formed when warm and moist air moves across cold surface such as pacific coast in summer-always involves movement of air
Term
 upslope fog
Definition
 -fog that forms as moist air flows up elevated plain/hill/mountain
Term
 evaporation fog
Definition
 -like moist air from your mouth on cold day-fog that forms from two unsaturated masses of air-also when cold air moves over warm water (steam fog)-steam fog is very short lived
Term
Definition
 -air from ocean bends into headlands and lifts, bringing up fog
Term
 Lv/Lf
Definition
 Lv-latent heat of vaporization... nearly 600calories/g-released when you get Lc below Td **DEW warms environment... Temp rarely cools below dewpointLf= latent heat of fusion... 80cal/g-freezing releases Lf*when it snows you get Lv plus Lf
Term
 Howard's latin for clouds
Definition
 -stratus... sheet-like-cirrus... wispy - 'a curl of hair'-cumulus .... 'heap'-nimbus ... 'violent rain'Abercrombie and Hildebrondsson have current system of classification
Term
 High, Med, Low, and VD clouds
Definition
 High... cirrus/cirrocumulus/cirrostratus-above 20000ft (6km)... mostly ice crystalsMed... Altocumulus/Altostratus-bases b/w 2000-7000m... mostly waterLow... Nimbostratus/stratocumulus/stratus-bases below 2000m...all waterVD... cumulus/cumulonimbus
Term
 cirrus
Definition
 -most common high cloud- thin and whispy... 'mares tails'-white patch with feathery wisp at a tail-no precip-formation high level ascent
Term
 cirrocumulus
Definition
 -small rounded white puffs-occur individually or in rows... rippling appearance-resemble scales of fish... no precipitation-formation through convection-internal instability
Term
 cirrostratus
Definition
 -thin and sheetlike... often cover entire sky-can see sun/moon through them... halo effect-typically indicate advance of storm-no precip-formation through widespread upper level ascent
Term
 altocumulus
Definition
 -gray puffy masses... sometimes parallel waves or bands-one part of cloud is darker than other-appear larger that cirrocumulus-precip is virga or light showers-formation through convection and wave flow near mountins
Term
 altostratus
Definition
 -bluegray or gray cloud that often covers entire sky-sun may be dimly visible as a round disk-dif from cirrostratus in grayness, height, and dimness of sun-also will never get a halo; you won't see your shadow-rain or snow may form-widespread ascent formation
Term
 nimbostratus
Definition
 -dark, gray wet looking cloud layer... associated with continuous rain or snow-precip usually light or moderate-formation widespread ascent
Term
 stratocumulus
Definition
 -low and lumpy cloud layer... rows or patches-light to dark gray... usually scattering cumulus cloud-bigger elements that altocumulus and have lower base-blue sky visible between them, yet they are closer together than cumulus-light rain/drizzzle/snow
Term
 stratus
Definition
 -uniform grayish cloud... often covers entire sky-resembles fog that does not reach ground-usually no precip-but sometimes light drizzle-occurs near coastal waters in summer-formation low level ascent
Term
 cumulus
Definition
 -piece of floating cotton with sharp outlines and flat base...different from stratocumulus in that they are very detached-showers of rain or snow-formation from convection (surface heating or instability)
Term
 cumulonimbus
Definition
 -thunderstorm cloud with anvil top-all kinds of precip
Term
 types of cumulus
Definition
 -cumulus humilis - only slight vertical growth... associated with fair weather-cumulus fractus - small and appear as broken fragments with ragged edges-cumulus congestus - towering cumulus, with head resembling head of cauliflower.... almost cumulonimbus
Term
 some unusual clouds
Definition
 -lenticular - shape of lens... formed due to mist air crossing mountain barrier forming waves (stack of pancakes or hovering spaceship)-pileus - cap clouds- usually resembles a silken scarf capping a towering cumulus cloud-contrail - cirrus like trail of condensed vapor formed by jets flying at high altitudes... due to heat exhaust with cold air... stay for hours if RH high-nacreous clouds - soft pearly clouds above troposphere... form in stratosphere @ 30+ km-noctilucent clouds - upper mesosphere 75+km.. appear bright against darker background... tiny ice crystals... water from dissolved meteors
Term
Definition
 -when air parcel expands/cools or compresses/warms with no exchange of heat with outside surroundings
Term
Definition
 -only applies to unsaturated air-10C/km (1C/100m)-if rising air cools to dew point, further lifting beyond this point results in condensation
Term
Definition
 -lesser rate than 10C as condensation offsets this cooling-approx 6C, but fluctuates a lot depending upon amount of vapor density-** rate at which rising or sinking saturated air changes T is less than dry adiabatic rate
Term
 stable conditions
Definition
 -rising air is colder than environment (resists upward displacement)-clouds in stable environment are all 4 stratus cloud types... flat clouds-atmosphere is stable when environmental lapse rate is small (gets cold slowly going up)-atmosphere generally most stable at sunrise...due to ground cooling... nighttime radiational cooling, influx of cold surface wind, air moving over a cold surface-stable air tends to form excellent conditions for high pollution
Term
 unstable atmosphere
Definition
 -rising air is warmer (less dense) than surroundings-associated with severe weather & thunderstorms-very large lapse rate (air T decreases rapidly)-usually occurs during very warm periods (summertime, not winter)-unstable air tends to be very well mixed
Term
 subsidence inversion
Definition
 -inversion formed by slow sinking air
Term
 3 kinds of atmospheric conditions
Definition
 1)stable atmosphere2)unstable atmosphere3)conditionally stable atmosphere (dry and moist adiabatic lapse rates.... rising air may or may not overcome stable area)
Term
 instability on different scales
Definition
 -convection - 5km - pops up to cumulus cloud-orographic uplift - 150km - topography lifts-low pressure - 500km - convergence of air -along fronts - 1500km - over cold fronts (lifts)
Term
 ambient lapse rate
Definition
 another term for environmental lapse rate
Term
 conditional stability
Definition
 -forced up at first (stable) but breaks barrier at moist lapse rate so instability occurs higher upAVERAGE GLOBAL LAPSE RATE IS 6C/KM***EXISTS WHENEVER THE ENVIRONMENTAL LAPSE RATE IS IN BETWEEN MOIST AND DRY LAPSE RATES
Term
Definition
 -lapse rate when environmental lapse rate exceeds dry lapse rate-leads to unstable conditions
Term
 level of free convection
Definition
 -level in atmosphere where air parcel becomes warmer than the air surrounding it (the switching spot in a conditionally stable atmosphere)
Term
 leeward
Definition
 side of mountain range where rain shadow exists-lenticular clouds may form on this side-rotor clouds form here as well
Term
 precipitation
Definition
 -any form of water that falls from a cloud and reaches the ground-typical raindrop is 100X diameter of a cloud droplet, and 10000X condensation nucleus
Term
 warm clouds
Definition
 -above freezing temperatures at all levels-
Term
 factors for rain droplet formation
Definition
 -liquid water content-cloud thickness-range of droplet sizes-updrafts of cloud-electric charge of droplets and electric field in cloud
Term
 Bergeron process
Definition
 -also called ice-crystal process-proposes that both ice crystals and liquid cloud droplets must coexist in clouds at temperatures below freezing-these are COLD CLOUDS-if not many ice nuclei exist, clouds in freezing areas are mostly water******the saturation vapor pressure just above water surface is greater that saturation vapor pressure above ice surface.... this causes vapor molecules to move from droplet to ice crystal
Term
 accretion
Definition
 -process of ice crystals growing larger as they collide with super-cooled cloud droplets*a snowflake is an aggregate of the crystals
Term
 cloud seeding
Definition
 -introduction of artificial substance into a cloud for the purpose of either modifying its development or increasing precipitation-silver iodide is a good seeder- cnatural seeding may occur as ice crystals fall from cirrus clouds into cumulus and act as nuclei
Term
 types of "rain"
Definition
 rain-diameter greater than 0.5mmdrizzle-diameter less than 0.5mmvirga-tiny evaporating streaks of precipitationshower-rain in a downdraftcloudburst-excessively heavy shower
Term
 types of snow
Definition
 -fallstreaks- ice crystals/snowflakes that fall from high cirrus clouds .....large snowflakes associated with moist air and T near freezing-dendrite - fernlike branch shape snowflake... most common-flurries - snow falling from developing cumulus clouds-snow squall - more intense snow shower-sleet - tiny transparent ice pellet... occurs when snowflake melts and then refreezes-freezing rain - rain that freezes immediately upon contact-rime - white/milky granular ice formed when supercooled cloud/fog droplets strike on object whose T is below freezing-snow grains - solid equiv of drizzle-snow pellets - white opaque grains of ice about the size of an average raindrop - are brittle, crunchy, and bounce
Term
 hailstones/hailstreaks
Definition
 -pieces of ice ... largest up to 7 inches-produced in cumulonimbus when graupel acts as nuclei for accretion-must remain in cloud for 5-10 minutes to get golf-ball sized stone-hailstreaks are long and narrow bands where clouds deposit hail-efforts to prevent hail include introducing many nuclei (seeding)
Term
 ways of measuring precipitation
Definition
 1)standard rain gauge- funnel shaped collector attached to measuring tube2)tipping bucket - more accurate... loses a little rainfall during each tip3)weighing type - extremely accurate... weighs rainfall
Term
 water equivalent
Definition
 -generally 10 inches snow will melt to 1 inch water... though this varies GREATLY
Term