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Atmospheric Moisture & Clouds. Water in the Atmosphere. Water vapor is the source of all condensation and precipitation Essentially all water on Earth is conserved –> water cycle. Changes of State. Changing states requires energy transfer in the form of heat
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Water in the Atmosphere • Water vapor is the source of all condensation and precipitation • Essentially all water on Earth is conserved –> water cycle
Changes of State • Changing states requires energy transfer in the form of heat • Water has a high Specific Heat • Which means a large amount of energy is gained or lost as water changes temperature
Phase changes requiring…. • The addition of heat: • Melting • Evaporation • Sublimation – solid directly to gas • The removal of heat • Freezing • Condensation • Deposition – gas directly to solid
Humidity • Saturation – the maximum quantity of water vapor air can hold at a given temperature and pressure • Warm air can hold more water vapor than cool air
Relative Humidity (RH) • Ratio of the air’s actual water vapor content compared with the amount of water air can hold at that temperature and pressure • 2 ways to change RH • 1. Add or remove water vapor • 2. Change the temperature • Higher temp: ________________ • Lower temp: ________________
Relative Humidity (RH) (cont.) • Once air is saturated further cooling causes condensation (ex: dew, clouds) • Condensation nuclei: tiny bits on which water condesates (dust, smoke, salt)
Relative Humidity (RH) (cont.) • Measured using a psychrometer
Dew Point • Dew Point –Temperature to which air would have to be cooled for saturation to occur • Depends on? __________________ • For every 10° C increase in temp. the amount of water vapor for saturation double • High dew points indicate moist air • Low dew point indicate dry air
Using RH and Dew point • Dew point can found by using the RH • When air temp. and dew point are close: RH is high • When air temp. and dew point are far apart: Rh is low
AdiabaticTemperature Changes: • -When air expands: ______________ • -When air is compressed: ________
Lifting Air • Orographic:elevated terrains such as mountains act as barriers to air flow • Frontal Wedging: warmer, less dense air rises over colder, denser air • Convergence: when air flows in from multiple directions, lifting results (Ex. Florida) • Convective:unequal heating of earth’s surface creates ‘pockets’ of rising air (parking lots)
Atmosphere Stability • Stable air remains in its position • Unstable air tends to rise • Most stable occurs with a temperature inversion which means air temp increases as you go up in altitude • Stability & Weather: • Stable air: _________________________________ • Unstable air: ________________________________
Clouds • Classified based on form and height • Cirrus: high, white, thin • Cumulus: rounded with flat base • Stratus: sheets or layers of clouds • Nimbus: rainy clouds • Combinations of these are used to describe any cloud (Cumulonimbus= ____________________)