Chapter 6: Stability and Cloud Development

List four primary ways clouds form, and describe the formation of one cloud type by each method.

1. Surface heating and free convection: Thermals are a bubble of hot air that rises. As more and more rise the air cools to it saturation point causing moisture to condense forming a cloud. 2. Uplift along topography: Air moves horizontally across the surface. It cannot get through things it will encounter so the air is forced up. Air goes up cools and forms clouds. 3. Widespread ascent due to convergence of surface air: Air masses coming together forces air up where cooling happens forming clouds 4. Uplift along weather fronts: Forced lifting along warm and cold weather fronts causes air to be forced up where cooling happens from clouds.

Explain the difference between enironmental lapse rate and dry adiabatic rate?

The enviromental lapse rate is the rate at which the air temperature changes as you increase in elevation. Unlike the dry rate, this is the rate of change of temperature of the actual air.

Why are moist and dry adiabatic rates of cooling different?

The moist adiabatic rate of cooling is usually less than the dry rate because as a parcel of moist air expands, the water droplets in it will evaporate, taking heat with them. This helps to offset the heat generated from the parcel expanding. The same principle applies to compressing the parcel and condensation.

Why do cumulonimbus clouds often have flat tops?

The reason cumulonimbus clouds have flat tops is because the tropoause, the interface between the troposphere and the stratosphere, is often stable. This area prevents the cloud from growing and foces the cloud outwards

Why are cumulus clouds more frequently observed during the afternoon than at night?

The reason you see these kinds of clouds at night is due to daytime heating. The air the was heated during the day then raises and become cumulus clouds at night. ***because of daytime solar heating. As the Sun heats the Earth's surface, thermals are created, and air rises.***

Explain why an inversion represents an absolutely stable atmopshere.

With an inversion, warm air overlies cold air; the air is becoming colder while the air around it is getting warmer. This cause the rising air to sink, creating stability.

If the atmosphere is conditionally unstable, What condition is necessary to bring on instability?

Instability would result when unsaturated air is lifted and then becomes saturated in the process.

How and why does lifitng or lowering a layer of air change its stability?

Lifing or lowering a layer of air changes causes the air to stretch out or compact as the air density aloft increases or decreases. When the air stretches out, it colles more quickly. The air at the top of the layer will be cooler than the air at the bottom, which steepens the envrionemtal lapse rate and increases instability.

List and explain several process by which an unstable atmosphere can be made stable.

One of the ways the atmosphere could become stable is by the air cooling and becoming less dense and matching the air around it.

Explain why rain shadows form on the leeward side of mountains?

Precipitation falls on the windward side of the mountain.

List and explain several processes by which a stable atmosphere can be made unstable

A stable atmosphere can be made unstable when the environmental lapse rate steepens, which occurs when air temperature drops rapidly with increasing height: Causes include: Cooling of the air aloft: -Winds bringing in colder air (cold advection) - Clouds (or the air) emitting infrared radiation to space (radiational cooling) -Warming of surface air -Daytime solar heating of the surface -An influx of warm air brought in by the wind (warm advection) -Air moving over a warm surface

What is a stable atmosphere and how can it form?

A stable atmosphere is when the environmental lapse rate is less than the moist/dry adiabatic rates, meaning that as an air parcel rises, it cools faster than the air around it, meaning it will want to sink back down to the level it was originally at. A stable atmosphere forms when the surface cools(through radiational cooling at night; an influx of cold surface air brought in by the wind(cold advection); or from air moving over a cold surface).

What type of cloud formation are typically assoicated a warm front an cold front?

Air that is forced to ride up and over the gentle slope of a warm front will produce layered clouds in the stratus category because the atmosphere is mainly stable. Air that is forced upward along a more aggressive cold front will tend to build vertically and be in the cumulus category because the atmosphere is mainly unstable.

What is an adiabatic process?

An adiabatic process is when a parcel of air expands and cools, or compresses and warms, with no interchange of heat with its surroundings

Why are thre usually large spaces of blue sky between cumulus clouds?

Because the thermals that form them on the ground are usually shaded/etc by the cloud that was just formed, and take time for the thermals to build up again.

Describe the general characteristics of clouds assoicated with stable and unstable atmopshere

Clouds in a stable atmopshere tend to spread out horizonatally, resulting in cirrostratus, altostraus, nimbostratus, or stratus forming in the stable air. Clouds are more likely to grow vertically in an unstable/conditionally unstable atmosphere, as the warm air parcel from the ground tends to keep rising upwards.

Under what conditions would the most adiabatic rate of cooling be almost equal to the dry adiabtic rate?

When the air that is rising is very cool, less moisture is generated as it rises, causing the moist adiabatic rate to rise and almost be equal to the dry adiabatic rate.