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58 terms

ESC1000 Chapter 17 Moisture, Clouds and Precipitation

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Melting
Substance solid transforms to liquid. A cooling process
Cooling process
Is melting a heating or cooling process?
Freezing
liquid transforms to solid. A heating process.
Heating process
Is freezing a heating or cooling process?
Evaporation
liquid transforms to vapour. A cooling process
Condensation
Vapour transforms to liquid. A heating process.
Sublimation
A solid transforms to a gas, skipping the liquid phase. A cooling process.
Deposition
A gas transforms to a solid. A heating process.
Humidity
the amount of water vapor in air.
Higher
When temperature is higher, the amount of water vapor air can hold is _______
Lower
When temperature is lower, the amount of water vapor air can hold is _______.
Unsaturated
When a given parcel of air is holding less water than it can actually hold it is___________.
Saturated
When a given parcel of air is holding all the water vapor it can hold, it is _________.
Mixing ratio
specific humidity
Specific humidity
Ratio of the amount of water vapour in air by weight, compared to the mass of air it is in. Not affected by temperature.
Absolute humidity
Ratio of the amount of water vapour in air by volume, compared to the volume of air it is in. Not affected by temperature.
Relative humidity
Ratio of the amount of water vapour in air compared to the amount needed to saturate the air at the same temperature. Given as a percentage. Is strongly affected by temperature.
Relative humidity
how much water the air is holding relative to the amount is can potentially hold, its capacity. Is strongly affected by temperature.
Increases
What happens to relative humidity when temperature increases?
Decreases
What happens to the capacity of air to hold water vapour when temperature decreases?
Increases
What happens to relative humidity when the water vapour content of the air stays the same, but the temperature drops?
Dew point
The temperature that a parcel of unsaturated air would have to fall to, in order to become saturated. Given as a temperature.
Hygrometer
A device to measure humidity
Sling psychrometer
a type of hygrometer.
Adiabatic temperature change
When a gas changes temperature because of a pressure change (either expansion or compression).
Orographic lifting
When air is forced up and over mountains
Frontal wedging
weather process where a body of cold air meets hot air, and the hot air is forced up and over the cold air, it expands, cools, condensation occurs and clouds form.
Convective lifting
weather process where the sun heats the land surface, which heats the adjacent air, and then the heated air rises.
Thermal
another name for convective lifting.
Convergence
weather process where wind (with air of similar temperatures) from two directions meet and the only way for the air to go is up.
Cirrus
Cloud that is high level and wispy or light and patchy in form, made of ice crystals and is always up high.
Cumulus
Form of cloud that is puff balls, often with a flat base (but can lose flat base due to air circulation).
Stratus
Form of cloud in sheets or layers, that may cover the whole sky, and doesn't have separate clouds.
Cirrocumulus
Form of cloud that is high in level and puff ball in form.
Cirrocumulus
High level puffy ball clouds.
Cirrostratus
high level, very light layers of cloud.
Alto
general term for clouds that are at mid level
Altocumulus
mid-level puffball clouds.
Altocumulus
clouds that are mid-level, and bigger and denser than cirrocumulus.
Altostratus
clouds at mid-level that form a light sheet that lets the sun or moon show as a bright spot.
stratus
general term for clouds that are low level
stratus
low level layers of cloud that often cover much of the sky
stratocumulus
clouds that are low-level layers of cumulus clouds, that begin to touch each other and fuse.
Nimbostratus
clouds that are low-level, uniform layer, usually very dark, that bring strong precipitation.
Nimbus
general term for clouds that means rainy in Latin.
Cumulonimbus
Clouds that are the product of growth of cumulus which can form huge thunderheads.
Fog
a cloud that forms at or near the ground.
Mist
precipitation that reaches the surface in liquid drops of the smallest size. 0.005-0.05mm diameter.
Drizzle
precipitation that reaches the surface in liquid form, drops 0.05-0.5mm diameter.
Rain
precipitation that reaches the surface in liquid form, drops 0.5-5mm diameter.
Snow
precipitation that reaches the surface in form of ice crystals or aggregates of crystals
Sleet
precipitation that reaches the surface in form of small ice particles. Often falls as rain but then passes through a cold layer that freezes the drops.
Hail
precipitation that reaches the surface in form of larger pieces of ice. Formed in cumulonimbus clouds in updrafts of up to 100mph.
Glaze
forms when rain freezes as it hits a freezing surface, forming a thin coating of ice. Eg black ice.
Rime
deposit of ice crystals that forms directly on cold surfaces from fog.
Graupel
Soft hail, which forms when rime coats snowflakes on their way down.
Bergeron Process
formation of precipitation, where water condenses, and freezes, then falls frozen or melted as rain.
Collision-coalescence process
formation of precipitation, where tiny droplets accumulate, fall, and collide with other small droplets until rain drops form and fall.