1. For absolutely stable air both dry and moist lapse rates are higher than the ELP
e.g. DALR = 100C/1000m
MALR= 60C/1000m
ELR = 40C/1000
For absolutely unstable air both moist and dry lapse rates are lower than the ELP
e.g MALR =60C/1000m
DALR=100C/1000m
ELR= C/1000m
For Conditionally unstable air, the ELP lies between the moist and dry lapse rates
e.g. DALR=100C/1000m
ELR = 70C/1000m
MALR = 60C/1000m

2. SO WHAT CAN CAUSE THE AIR’S STABILITY TO CHANGE?
Changing the environmental lapse rate will potentially change stability. This can happen by:
1. Cooling of the air aloft
(a) winds bringing in colder air (cold air advection)
(b) clouds or air emitting infrared radiation to space (radiational cooling)
2. Warming of the surface air
(a) daytime solar heating of the surface
(b) winds bringing in warm air (warm advection)
(c) air moving over a warm surface

3. Environmental lapse rate
1. Cooling of the air aloft
(a) winds bringing in colder air (cold air advection)
(b) clouds or air emitting infrared radiation to space (radiational cooling)
2. The warming of the surface air
(a) daytime solar heating of the surface
(b) winds bringing in warm air (warm advection)
(c) air moving over a warm surface

4. HOW HIGH THE MOON? I MEAN HOW HIGH THE CLOUD?

6. The predominate
cloud type for
High clouds.
Each type’s
symbol is found
in the table.

7. The predominate
cloud type for
medium clouds.
Each type’s
Symbol is found
in the table.

8. The predominate cloud type low clouds
The predominate cloud type low clouds. Each type’s symbol is found in the table.

9. 1mμ =one
millionth of
a meter or
one micrometer

11. 1mμ =one
millionth of
a meter or
one micrometer

16. Water vapor pressure higher over liquid than ice

17. THE ICE CRYSTAL PROCESSOr
BERGERON PROCESS
The greater number of water
Molecules around the liquid droplet
causes molecules to diffuse from the
liquid droplet toward the ice crystal.
The ice crystal absorbs the water
vapor and grows larger, while the
water droplet grows smaller.

18. SOME TERMS
Condensation nuclei = 0.2 μm (more over the land than ocean)
Cloud Droplet = about 20 μm
Typical Raindrop = about 2000 μm
Collisions/coalescence = collisions between cloud droplets makes bigger droplets
Ice nuclei: needed to commence the freezing process at sub 0 temperatures
Deposition nuclei: nuclei that allow water vapor to deposit on their surfaces
Freezing nuclei: promote freezing of super cooled droplets by way of a liquid phase
Accretion: Ice crystals collide with supercool droplets – forms graupel
Aggregation: ice crystals collide and stick together – results in snowflake
Rime: the deposit of ice crystals formed by the freezing of supercooled fog or cloud droplets on
objects whose surface temperature is below freezing. This can happen on trees, like pine
where the needles act as freezing nuclei

20. NOTE: This is a chart from the U.S. Weather Service which does not use
the metric system so the measurement is in “inches” rather than
“centimeters”

23. * US Weather Service does not use the metric system, so the distance is in miles.

27. HAILSTONE PHOTGRAPHED
WITH REGULAR LIGHT
SHOWING LAYERS
HAILSTONE PHOTGRAPHED
WITH POLARIZED LIGHT
SHOWING LAYERS

28. NOTE THE WEATHER SYMBOL CODES FOR THE PRECIPITATION TYPES

29. A MORE
COMPLETE SET
OF SYMBOLS FOR
PRECIPITATION