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36 Cards in this Set
- Front
- Back
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Describe the composition of clouds
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- water droplets
- supercooled water droplets - ice crystals in suspension in the atmosphere 109.1.1 |
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Describe the Dry Adiabatic Lapse Rate and the Saturated Adiabatic Lapse Rate
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- DALR is 10C/km or 3C/1000ft
- SALR is 5C/km or 1.5C/1000ft 109.1.2 |
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Describe the relationship between the height of cloud base and the temperature-dew point spread
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The smaller the spread, the more humid the air, and the lower the cloud base. The bigger the spread, the dryer the air, and the higher the cloud base
109.1.3 |
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Describe the relationship between cloud height and vertical currents
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- in stable air, vertical motion will cease when lifting agent ceases to operate
- in unstable air, vertical motion will cease once temp of rising air reaches equilibrium with surrounding air temp 109.1.3 |
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Relate cloud type to stable and unstable conditions
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Stable: Unstable:
- CI CC CS - ACC AC AS CF CU TCU CB NS ST SF SC 109.1.4 |
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State the 5 lifting processes
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- convection
- orographic lift - convergence - frontal lift - mechanical turbulence 109.1.5 |
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List the factors which contribute to the formation and dissipation of clouds formed by orographic lift
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Formation:
- slope steepness - terrain height - wind direction and speed - humidity - stability Dissipation: - change of air mass - change of wind direction/speed 109.1.6 |
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List the factors which contribute to the formation and dissipation of clouds formed by mechanical turbulence
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Formation:
- rough ground - wind strength - humidity - stability Dissipation: - change of air mass - decrease in wind speed 109.1.6 |
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List the factors which contribute to the formation and dissipation of clouds formed by convergence
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Formation:
- horizontal and vertical extent of convergence - humidity - stability Dissipation: - change of air mass - filling of low 109.1.6 |
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Define: Precipitation
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Any product of condensation/sublimation of atmospheric water vapor which is deposited on earth's surface
109.2.1 |
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Define: Liquid cloud particles
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- water droplets greater than 0C
109.2.1 |
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Define: Supercooled cloud particles
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- water droplets remaining in liquid state at temps below the freezing point, but freeze on impact
109.2.1 |
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Define: Solid cloud particles
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- water droplets that have frozen into ice crystals, or ice crystals formed directly by sublimation
109.2.1 |
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Describe the ice crystal process (Bergeron Effect) in the formation of precipitation
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When ice crystals and supercooled water droplets are present together, evaporation from the droplets is sublimated on the ice crystals. This continues until ice crystals are sufficiently heavy to fall.
Occurs in temps -10C to -40C 109.2.2 |
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Describe the collision process in the formation of precipitation
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Ice crystals grow by colliding with other crystals, larger ones tending to capture smaller ones in their path.
109.2.2 |
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Describe DZ
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Drizzle
- fine drops of water that appear to float in the air - from stratus cloud - from very stable moist air 109.2.3 |
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Describe FZDZ
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Freezing drizzle
- drizzle drops that freeze on contact with the ground - from stratus cloud - from very stable moist air 109.2.3 |
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Describe SG
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Snow grains
- very small white and opaque grains of ice - from stratus cloud - from very stable moist air 109.2.3 |
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Describe RA/SHRA
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Rain
- liquid drops of water - from ACC, TCU, CB, NS, AS, SC,AC - the more unstable the conditions, the larger the drops |
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Describe FZRA
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Freezing rain
- rain drops that freeze on impact with the ground - from NS, AS - needs above freezing air over top of below freezing air 109.2.3 |
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Describe PL
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Ice pellets type "A"
- transparent spheres of ice, 5mm or less - from NS, AS - snow flakes that have melted and refrozen 109.2.3 |
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Describe SHPL
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Ice pellets type "B"
- opaque spherical or irregular shaped ice, 5mm or less - from TCU, CB - pellets of snow encased in thin layer of ice 109.2.3 |
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Describe SHGR
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Hail
- irregular shaped lumps of ice with clear and opaque layers, 5mm to 50mm - from mature CB - from very unstable conditions 109.2.3 |
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Describe SHGS (summer)
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Small hail
- irregular shaped lumps of ice with clear and opaque layers, less than 5mm - from mature CB - from very unstable conditions 109.2.3 |
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Describe SHGS (winter)
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Snow pellets
- white and opaque fragile spheres or cones of ice, 2mm to 5mm - from winter CU, TCU, CB, SC - from unstable conditions 109.2.3 |
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Describe SN/SHSN
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Snow
- white branched hexagonal or star-like ice crystals, frequently interlocked to form large flakes - from CU, TCU, CB, ACC, NS, AS, AC, SC - formed by ice crystal or collision processes 109.2.3 |
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Describe IC
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Ice crystals
- unbranched needle/column/plate ice crystals appearing to be suspended in the air - from sublimation - from stable and very cold (-25C or less) conditions 109.2.3 |
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Explain the difference between intermittent, continuous, and showery precipitation
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Continuous:
- continues without a break since its beginning - falls from clouds formed in stable air Intermittent: - significant variations in water content of cloud in the horizontal, or evaporation on descent - will stop and restart - falls from thinner clouds - from clouds formed in stable air Showery: - usually begin and end abruptly - rapid fluctuations in intensity - noticeable brightening of sky between showers - falls from cumuliform cloud 109.2.4 |
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Define fog and state its composition
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A suspension of water droplets, supercooled water droplets, or ice crystals, at the surface of the earth
109.3.1 |
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List the three conditions required for the formation of fog
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- high relative humidity
- condensation nuclei - cooling of air AND/OR addition of water vapor 109.3.2 |
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Name the five types of fog
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- radiation
- advection - upslope - frontal - steam fog 109.3.3 |
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State the conditions required for the formation, duration, dissipation, and the characteristics of radiation fog
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Formation:
- clear night - light winds - high relative humidity - condensation nuclei Dissipation: - daytime heating - increasing winds - decreased relative humidity Characteristics: - forms or thickens at sunrise, often seen in early morning hours - drains into low lying areas - dissipates during morning, usually due to daytime heating - more common under highs/ridges - may be caused by aircraft 109.3.4 |
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State the conditions required for the formation, duration, dissipation, and the characteristics of advection fog
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Formation:
- advection of warm, humid air over cold surface - moderate winds - high relative humidity - condensation nuclei Dissipation: - increasing winds - wind direction change - daytime heating of ground Characteristics: - can cover large area - can persist for long periods - in warm sector of frontal waves - can be blocked by higher terrain - thins with daytime heating of ground - daytime heating has little effect over water 109.3.4 |
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State the conditions required for the formation, duration, dissipation, and the characteristics of upslope fog
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Formation:
- orographic lift - moderate winds - high relative humidity - condensation nuclei Dissipation: - daytime heating - increasing winds and lifting - change in wind direction Characteristics: - persists until air mass or wind direction change - dissipates on leeward side of upslope 109.3.4 |
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State the conditions required for the formation, duration, dissipation, and the characteristics of frontal fog
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Formation:
- warm air over cold air - frontal precipitation - high relative humidity - condensation nuclei Dissipation: - movement of front and pressure pattern - precipitation ceases Characteristics: - can form rapidly 109.3.4 |
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State the conditions required for the formation, duration, dissipation, and the characteristics of steam fog
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Formation:
- cold air above warmer water - high relative humidity - condensation nuclei Dissipation: - daytime heating - change of air mass - freezing of open water Characteristics: - usually thin - only forms over water - can drift over land after formation - often forms over lakes/rivers on cold mornings - common in Arctic above leads in ice 109.3.4 |
