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37 Cards in this Set

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Saturated Air
evaporation and condensation are in equilibrium
Condensation occurs easier when
It is cold. Molecules move slower and it is easier for them to stick together.
Air parcel concept
an imaginary small body of air that is used to explain air behavior and characteristics.
Atmospheric water vapor content has been defined several different ways
These terms include absolute humidity, specific humidity, mixing ratio, vapor pressure, and relative humidity
Absolute humidity
(g/m3) – the mass of water vapor in a given volume of air. It can be thought of as density of water vapor in the air.
Specific humidity
(g/kg) – the ratio of the mass of water vapor in a given parcel to the total mass of air in the parcel.
Mixing ratio
(g/kg) – the ratio of the mass of water vapor in a given volume of air to the mass of dry air.
total air pressure
inside is equal to the sum of the pressures of the individual gases (78% nitrogen, 21% oxygen, and 1% water vapor)

So inside the parcel, nitrogen = 780 mb, oxygen = 210 mb, and water vapor = 10 mb.
Saturation vapor pressure
describes how much water vapor is necessary to make the air saturated at any given temperature.
Adiabatic Process
is when an air parcel cools by expansion or warms by compression with no exchange of heat from the the outside environment.
(cooling is expansion, going up. Warming is compressing, pushing down)
Dry Adiabatic Rate
the rate at which an “unsaturated” parcel is cooled or warmed adiabatically (adiabatic process). The dry adiabatic rate is 10°C per 1000 m or 5.5°F per 1000 ft and it remains constant.
Moist Adiabatic Rate
the rate at which a “saturated” parcel is cooled and warms with ascending or descending motion. This rate varies but it is less than the dry adiabatic rate due to latent heating from condensation offsetting the cooling. A commonly used value for the moist adiabatic rate is 6°C per 1000 m or 3.3°F per 1000 ft. This rate is not an adiabatic process due to latent heating
Environmental Lapse Rate
the rate at which ambient air temperature decreases with height. This rate can vary as well and must be measured by a radiosonde.
High Clouds
Cirr...
Low Clouds
Strat...
Nimbo...
Middle Clouds
Alto...
Vertical Development Clouds
Cumul...
stable atmosphere
goes back to normal
When cold air lies underneath warm air, this setup is considered to be a stable atmosphere
Adiabatic Process
is when an air parcel cools by expansion or warms by compression with no exchange of heat from the the outside environment. (cooling is expansion, going up. Warming is compressing, pushing down)
Dry Adiabatic Rate
the rate at which an “unsaturated” parcel is cooled or warmed adiabatically (adiabatic process). The dry adiabatic rate is 10°C per 1000 m or 5.5°F per 1000 ft and it remains constant.
Moist Adiabatic Rate
the rate at which a “saturated” parcel is cooled and warms with ascending or descending motion. This rate varies but it is less than the dry adiabatic rate due to latent heating from condensation offsetting the cooling. A commonly used value for the moist adiabatic rate is 6°C per 1000 m or 3.3°F per 1000 ft. This rate is not an adiabatic process due to latent heating.
Environmental Lapse Rate
the rate at which ambient air temperature decreases with height. This rate can vary as well and must be measured by a radiosonde.
Surface air warming
1) daytime solar heating, 2) an influx of warm surface air brought on by wind (warm air advection), and 3) cooler air moving over a warm surface.
Cloud Development Triggers
(How air can be forced upward?)
Convection
Orographic uplift (topography)
Convergence of air
Lifting along weather fronts
Drop sizes
A raindrop is 100 times larger than a cloud droplet.
A cloud droplet is 100 times larger than a condensation nucleus.
1,000,000 cloud droplets = 1 raindrop
Collision and Coalescence occurs when
collision joining together small cloud droplets due to strong surface tension associated with a small drop and
b) coalescence attaching faster and larger droplets with smaller slower droplets.
1) clouds liquid water content (LWC)
2) droplet sizes
3) cloud thickness
4) updrafts
5) drop electrical charges.
warmer than -15°C to produce rain
Cold Cloud formation
Ice crystals have lower saturation vapor pressures than liquid droplets, creating a gradient of high to low water molecules from liquid to ice that encourages ice growth.

Now the droplet is out of equilibrium with its environment, the droplet evaporates to replenish the diminished supply of water vapor above it.

This process provide a continuous moisture source for the ice crystals to grow rapidly.

This growth is critical to the ice-crystal precipitation process.

So during the Bergeron process, ice crystal growth occurs at the expense of the surrounding water droplets.
seeder-feeder process
drop as ice crystals from one cloud through another cloud forming snow
rain
falling drop must have a diameter  0.5 mm
> 6 mm tends to breakup and form smaller droplets
Blizzard condition
Falling and/or blowing snow frequently reducing visibility to < 1/4 mile
sustained winds or frequent gusts > 35 mph
snow-to-liquid (SLR) ratio
On the average, every 10 inches of snow will melt down to about 1 inch of water (water equivalent).
Black Ice and Sleet
Environmental temperatures may reveal a warm zone between two freezing layers.

Snow falling into the warm zone will melt and either
a) fall as rain and refreeze on contact with the ground, or
b) refreeze and fall as sleet.
Rime
a granular ice, accumulates when supercooled cloud or fog droplets touch a frozen surface.
Snow grains
are precipitation in the form of very small, opaque grain of ice. Solid equivalent of drizzle.
Snow pellets
graupel
are white, opaque, approximately round ice particles between 2 and 5 mm in diameter that forms in a cloud either from the sticking together of ice crystals or from the process of accretion. Also more commonly known as graupel.
Standard Gauge
The precision rate is measured to the nearest 1/100 (0.01) of an inch. An mount less than that value is called a trace.

The 50 cm long tube, when filled, represents only 5 cm of total rainfall.
Recording Gauge
Tipping bucket and weighing rain gauges record precipitation rate at shorter time intervals, providing rain intensity data