MET 1010 0002 METEOROLOGY EXAM 2 STUDY GUIDE Dew Frost Dew forms on nights with ideal radiational cooling conditions Air near the surface cools to its dewpoint Water droplets form on grass and other low lying vegetation Air becomes saturated dewpoint depression 0 relative humidity 100 Condensation occurs When the dewpoint is below freezing we refer to it as the frost point Condensation nuclei are particles in the air onto which water vapor can condense salt dust volcanic ash etc Hygroscopic condensation nuclei are water seeking Most active in promoting condensation Hydrophobic condensation nuclei are water repelling Allow condensation to occur at relative humidity s of less than 100 Ex salt These condensation nuclei resist condensation even with relative humidity s of greater than 100 Ex oil Haze a layer of dust or salt particles occurs in the afternoon when the relative humidity is at a minimum low enough that Dry haze condensation does not occur even for the most hygroscopic condensation nuclei and floating particles remain small and selectively scatter some rays of sunlight on the condensation nuclei the particles increase and scatter sunlight much more efficiently occurs in the morning when the relative humidity is at a maximum as water collects Because the floating particles are larger they cause the visibility to be reduced to less than half of dry haze visibility Visibility may be reduced but not severely Wet haze a cloud on the ground Fog When the air approaches saturation condensation begins forming on condensation nuclei when millions or more floating water droplets form we get fog Radiation ground fog fog produced by radiational cooling shallow moist layer near the surface with drier air above radiational cooling has caused only the air near the surface to reach saturation leaving upper layers dry condensation occurs in the surface layer and fog forms a type of radiation fog that forms when cold air drains into a valley floor fog that occurs when warm moist air moves over a cold surface Valley fog Advection fog Advection fog tends to occur near the coast Advection the transfer of given air properties of air by horizontally moving it Clouds the result of warm moist air from the Gulf of Mexico being advected over Advection Radiation fog the cooler landmasses of the Gulf coast the cooler ground is the result of radiational cooling causing fog to form Upslope fog the fog that forms as moist air moves up along an elevated hill plain or mountain Occurs in winter and spring on the east side of the Rocky Mountains Evaporation mixing fog fog produced when two unsaturated air masses mix and create saturation Evaporation fog is seen when exhaling on a cold day or as steam fog low clouds 0 to 6500 feet Cloud Types 1 2 middle clouds 6500 to 26000 feet 3 high clouds 20000 to 60000 feet 4 clouds with vertical development within each group clouds are identified by appearance Stratus St layer sheet like Cumulus Cu heap puffy Cirrus Ci curl of hair wispy poorly defined edges Nimbus violent rain rain clouds high clouds composed mainly of ice crystals that move generally west to east Cirrus Ci Cirrocumulus Cc Cirrostratus Cs due to light refraction via ice crystals Altocumulus Ac Altostratus As entire sky with the sun faintly visible through the layer gloomy day clouds Nimbostratus Ns middle cloud semi puffy composed mainly of water droplets thin low cloud steady rainfall water droplet composed dark grey layer high clouds seen less frequently than cirrus mackerel sky fill gill appearance high clouds that form a thin sheet like layer can form halo around sun or moon middle clouds composed of water droplets and ice crystals that often cover the Scud ragged irregular shred of nimbostratus cloud low solid uniform layer of grey cloud cover no precipitation low flat and lumpy clouds that often occur near sunset low clouds limited vertical development fair weather clouds cumulus clouds with vertical development head of a cauliflower thunderstorm clouds flat top caused by the tropopause anvil caused by Stratus St Stratocumulus Sc Cumulus humilus Cu Cumulus congestus Tcu Cumulonimbus Cb upper level winds Unusual clouds Remember that clouds are the result of air that s saturated and has started condensing Many different ways to get condensation many different uncommon peculiar clouds found at crest of mountain wave formed by air forced over mountain to Lenticular saturation Pileus condensed Mammatus Nacreous cold water mother of pearl clouds cap cloud moist air deflected over cumulus congestus cumulonimbus and sinking air cloud sacs that hang beneath a cloud high latitudes stratospheric above altitudes of 30 kilometers made of ice and high clouds seen less frequently than cirrus mackerel sky fill gill appearance luminous light polar latitudes at twilight mesospheric altitudes of 75 90 Noctilucent kilometers made of ice crystals high clouds composed mainly of ice crystals that move generally west to east high clouds that form a thin sheet like layer can form halo around sun or moon Cirrus Ci Cirrocumulus Cc Cirrostratus Cs due to light refraction via ice crystals Altocumulus Ac Altostratus As entire sky with the sun faintly visible through the layer gloomy day clouds Nimbostratus Ns middle cloud semi puffy composed mainly of water droplets thin middle clouds composed of water droplets and ice crystals that often cover the low cloud steady rainfall water droplet composed dark grey layer ragged irregular shred of nimbostratus cloud low solid uniform layer of grey cloud cover no precipitation low flat and lumpy clouds that often occur near sunset low clouds limited vertical development fair weather clouds cumulus clouds with vertical development head of a cauliflower thunderstorm clouds flat top caused by the tropopause anvil caused by Scud Stratus St Stratocumulus Sc Cumulus humilus Cu Cumulus congestus Tcu Cumulonimbus Cb upper level winds Unusual clouds Remember that clouds are the result of air that s saturated and has started condensing Many different ways to get condensation many different uncommon peculiar clouds found at crest of mountain wave formed by air forced over mountain to cap cloud moist air deflected over cumulus congestus cumulonimbus and Lenticular saturation Pileus condensed Mammatus Nacreous cold water mother of pearl clouds Noctilucent kilometers made of ice crystals of an equilibrium state refers to the tendency of the system to return to equilibrium if luminous light polar
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