Meteorology 4 - 7

Front 1

Saturated Air

Back 1

evaporation and condensation are in equilibrium

Front 2

Condensation occurs easier when

Back 2

It is cold. Molecules move slower and it is easier for them to stick together.

Front 3

Air parcel concept

Back 3

an imaginary small body of air that is used to explain air behavior and characteristics.

Front 4

Atmospheric water vapor content has been defined several different ways

Back 4

These terms include absolute humidity, specific humidity, mixing ratio, vapor pressure, and relative humidity

Front 5

Absolute humidity

Back 5

(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.

Front 6

Specific humidity

Back 6

(g/kg) – the ratio of the mass of water vapor in a given parcel to the total mass of air in the parcel.

Front 7

Mixing ratio

Back 7

(g/kg) – the ratio of the mass of water vapor in a given volume of air to the mass of dry air.

Front 8

total air pressure

Back 8

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.

Front 9

Saturation vapor pressure

Back 9

describes how much water vapor is necessary to make the air saturated at any given temperature.

Front 10

Adiabatic Process

Back 10

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)

Front 11

Dry Adiabatic Rate

Back 11

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.

Front 12

Moist Adiabatic Rate

Back 12

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

Front 13

Environmental Lapse Rate

Back 13

the rate at which ambient air temperature decreases with height. This rate can vary as well and must be measured by a radiosonde.

Front 14

High Clouds

Back 14

Cirr...

Front 15

Low Clouds

Back 15

Strat...
Nimbo...

Front 16

Middle Clouds

Back 16

Alto...

Front 17

Vertical Development Clouds

Back 17

Cumul...

Front 18

stable atmosphere

Back 18

goes back to normal
When cold air lies underneath warm air, this setup is considered to be a stable atmosphere

Front 19

Adiabatic Process

Back 19

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)

Front 20

Dry Adiabatic Rate

Back 20

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.

Front 21

Moist Adiabatic Rate

Back 21

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.

Front 22

Environmental Lapse Rate

Back 22

the rate at which ambient air temperature decreases with height. This rate can vary as well and must be measured by a radiosonde.

Front 23

Surface air warming

Back 23

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.

Front 24

Cloud Development Triggers
(How air can be forced upward?)

Back 24

Convection
Orographic uplift (topography)
Convergence of air
Lifting along weather fronts

Front 25

Drop sizes

Back 25

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

Front 26

Collision and Coalescence occurs when

Back 26

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

Front 27

Cold Cloud formation

Back 27

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.

Front 28

seeder-feeder process

Back 28

drop as ice crystals from one cloud through another cloud forming snow

Front 29

rain

Back 29

falling drop must have a diameter  0.5 mm
> 6 mm tends to breakup and form smaller droplets

Front 30

Blizzard condition

Back 30

Falling and/or blowing snow frequently reducing visibility to < 1/4 mile
sustained winds or frequent gusts > 35 mph

Front 31

snow-to-liquid (SLR) ratio

Back 31

On the average, every 10 inches of snow will melt down to about 1 inch of water (water equivalent).

Front 32

Black Ice and Sleet

Back 32

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.

Front 33

Rime

Back 33

a granular ice, accumulates when supercooled cloud or fog droplets touch a frozen surface.

Front 34

Snow grains

Back 34

are precipitation in the form of very small, opaque grain of ice. Solid equivalent of drizzle.

Front 35

Snow pellets
graupel

Back 35

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.

Front 36

Standard Gauge

Back 36

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.

Front 37

Recording Gauge

Back 37

Tipping bucket and weighing rain gauges record precipitation rate at shorter time intervals, providing rain intensity data