Atmospheric Moisture (physical geography test 2) – Flashcards
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Evaporation
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water molecules going liquid to gas
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Condensation
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water molecules going gas to liquid
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Saturation
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the amount of evaporation is the same as condensation
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Sublimation
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ice turns directly to vapor and vice versa
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Humidity
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amount of water vapor in the air
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Absolute humidity
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is the density of the water vapor, or the mass of water in a cubic meter of air. as air heats up it expands so absoulte humidity decreases with heat.
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Relative humidity
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: amount of water vapor in air relative to maximum amount that can be in the air at a particular temperature RH = (amt. in air / max. amt.) x 100. • Maximum amount air can hold depends on air temperature—warmer air can hold more Since max. amount is in denominator, RH inversely proportional to temp. Often highest at dawn
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Dew point
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• Temperature at which air becomes saturated with water vapor Another measure of humidity When air temp = dew point, have 100% RH; air saturated with water vapor
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Diabatic processes
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remove energy from air
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Dew
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surface cools air
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Radiation fog
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night cooling of ground surface, air above cools
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Advection fog
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occurs when warm, moist air moves over a cooler surface. This is common in coastal areas where warmer, moister air over the water moves over the land during the night
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Adiabatic Processes
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- cooling not by removing energy, but changing the volume of air
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• Recall Environmental Lapse Rate
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air above is cooler because of lower pressure (not adiabatic)
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Dry adiabatic lapse rate
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- rising air cools at about 10°C/1000m, until saturation; lower pressure-larger volume-lower temp
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• Wet Adiabatic Lapse Rate
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- rising & saturated air cools at about 6°C/1000m
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Condensation nuclei
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dust, soot, and salts floating around in the air. cloud droplets form. • Air reaches 100% RH and continues to cool (becoming supersaturated)Water condenses on tiny particulates (condensation nuclei). Drops grow by collision & coalescence and fall when too heavy.
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Stratus
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thick layers at low altitudes. cover whole sky
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Cirrus
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are thin and wispy cirriiform clouds. mostly ice crystals
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Cumulus
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clouds are the puffy, cotton-ball types. If conditions are right, these generate thunderstorms.
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"Nimbus:"
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producing precipitation
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rainfall
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water falling in drops from vapor condensed in the atmosphere
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• Hail
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ice crystals fall and start to melt, then carried back up to add more water and re-freeze
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• Sleet
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rain falls through a cold layer and re-freezes before hitting ground
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• Freezing rain
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liquid when it hits, but freezes on ground
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snow
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forms by ice crystals gaining ice from the water vapor in the air and by colliding with supersaturated water drops, then the water freezes onto the ice
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Atmospheric stability
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- refers to how easily air will rise • Stable air: push it up and it drops down (gravity) • Unstable air: keeps rising (buoyant)
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Rainshadow effect
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the air losing much of its moisture crossing the mountain
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Convectional precipitation
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is caused by differential heating of the ground surface. The formation of precipitation due to surface heating of the air at the ground surface
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Orographic
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cloud formation that occurs when warm moist air is forced to rise up the side of a mountain
