Weather: Cloud Development

Front 1

What is an adiabatic process

Back 1

○ When a parcel of air expands and warms or compresses and cools with no interchange of heat with its outside surroundings

Front 2

2. How do you obtain the adiabatic lapse rate

Back 2

○ As long as the air is unsaturated (RH < 100%) it is 10 deg. C. per Km
○ IF it is Saturated it is apx. 6 deg C. per Km.

Front 3

3. Why are moist and dry rates different

Back 3

The lower rate attributed to moist adiabatic rate is due to the fact that moisture and condensation releases a latent heat

Front 4

How can the atmosphere be made more stable or unstable

Back 4

§ Nighttime radiational cooling
§ Influx of cold surface air brought in by wind
§ Air moving over cold surface
○ Therefore instable air can be made by either:
§ Daytime warming
§ Influx of warm air brought in by wind
§ Air moving over warm surface

Front 5

If the atmosphere is conditionally unstable what does this mean? what condition is condition is necessary to bring on instability?

Back 5

○ Dry stable air is somehow lifted to a level where it becomes saturate it may become instable

This occurs whenever the environmental lapse rate is between the dry and saturated lapse rates

Front 6

6. Why does an inversion represent an extremely stable atmosphere?

Back 6

Because it means that the cold air on the bottom is not going to rise and create instability

Front 7

What type of cloud would you find in a stable atmosphere? Instable?

Back 7

○ Stable=stratoform
○ Instable=cumuliform

Front 8

Why are cumulous clouds more common in the afternoon?

Back 8

○ Cumuliform clouds are likely to be present in the afternoon sky because this is the period in the day of the most rising and convection.

Front 9

Why are there usually large spaces of blue sky between cumulous clouds?

Back 9

As the condensation around the edges of a cumulous cloud evaporate the air becomes cooler. The cooler air sinks as the center of the cloud is lifted

Front 10

What are the four primary ways in which clouds form?

Back 10

a. Surface heating and free convection
b. Uplift along topography
c. Widespread ascent due to the flowing together of surface air
d. Uplift along weather fronts

Front 11

14. What is the primary difference between a cloud droplet and a rain droplet

Back 11

○ Size. A cloud droplet is 0.0002 mm and a rain drop is 0.02 mm

Front 12

Why don't typical cloud droplets reach the ground as rain?

Back 12

○ The small droplets typically evaporate in the dry air, or stay aloft since it doesn’t take a lot of updraft to keep them in the air

Front 13

16. How does the ice crystal process produce rain and what is the primary premise behind this process?

Back 13

○ Occurs in clouds that are below freezing where both water exists in liquid and solid state
○ Important in middle and high latitudes
○ Six water molecules will crystallize for some reason.
○ Once ice is formed, the vapor pressure is less in ice than liquid, so liquid water will move directly to the ice as a way of trying to obtain equilibrium
○ They can also take over supercooled water droplets if they collide with them, instantly turning them into ice through process known as accretion.
○ This icy matter eventually can coalesce into snowflakes which will melt before hitting the ground if it's warm enough

Front 14

17. Explain the collision coalescence model

Back 14

○ A large nucleus produces a larger rain drop which falls relatively quickly since it falls fast, it collides with more rain drops and cloud droplets. However, collision does not always result in coalescence
○ It is possible that coalescence occurs because of electrical charges between drops. They are more frequent in thunderstorms where there is a large amount of electricity.
○ This process is only known to occur in clouds with warmer tops (above -15 C./ 5F)

Front 15

What is the main principal behind cloud seeding?

Back 15

○ By injecting a cloud with tiny particles that act as nuclei, it is possible to make droplets grow larger enough to fall to the ground in the prom of precipitation.

Front 16

19. How can clouds be seeded naturally?

Back 16

○ If a cirroform cloud is situated directly above a cloud below, small ice particles can fall into the lower cloud and mix with super-cooled water droplets

Front 17

20. What's the difference between rain and drizzle?

Back 17

○ A rain drop has to be 0.5 mm or bigger, anything smaller is drizzle

Front 18

21. Why does heavy rain fall from cumuliform clouds and steady drizzle fall from stratoform?

Back 18

The rain associated with cumuliform clouds is bigger because it has more distance to accrete with other drop, whereas stratiform drops are smaller because they come froim lateral clouds

Front 19

22. Why is it never too cold to snow?

Back 19

○ Air always contains some water vapor that could become snow
○ Usually associate cold air with no snow because the coldest days are clear and dry

Front 20

23. How do you distinguish between virga and fall streaks?

Back 20

○ Virga are evaporating streaks of precipitation and fall streaks are ice crystals or snow flakes falling from cirrus clouds that turn into vapor as they reach lower/warmer elevations

Front 21

What is the difference between freezing rain and sleet?

Back 21

○ Sleet starts off as a snow flake, melts, then refreezes before coming t to the surface
○ Freezing rain melts, then re-freezes once it hits the surface