403.1a - composition, formation, and dissipation of clouds

Clouds are composed of tiny "visible" water droplets (in the order of _____).

20 micrometers or 0.02mm

Clouds appear when the temperature is _____ or when _____ are suspended in the atmosphere when the temperature is below 0°C.

above 0°C, ice crystals

What are the three main factors that determine cloud characteristics?

• Temperature of the air

• Stability of the air

• Moisture available

What does the temperature of the air determine?

The type of droplet

What does the stability of the air determine?

The type of cloud

What does the moisture available determine?

The thickness of cloud

Why is the calculation of the cloud base of “stratiform” clouds not possible using the temperature/dew point spread?

Because there is no rising air

When is the condensation level (or saturation level) of a rising column of air reached?

When the air temperature and the dew point temperature in the rising column of air are equal

The altitude of ______ determines the height of the cloud base

condensation level

What determines the dew point temperature?

The actual moisture content of the air

In unstable air, the vertical extent of the cloud can be much higher than that associated with stable air.

This is due to the moist air being _______ into the atmosphere.

pushed or driven further up

True or False: The cloud base will always form at the condensation level

True

The top of the cloud is impacted by _______ at altitude.

whatever vertical motion

If the air is stable, vertical motion ______ when the lifting agent ______.

will cease, ceases to operate

If air is stable, what will happen to the vertical motion of air?

It will continue until the temperature of the air reaches equilibrium with the surrounding air.

When strong inversions exist, upward vertical currents _____.

tend to be blocked

List the 9 stratiform/layer type clouds formed in stable conditions:

CI, CC, CS, AC, AS, NS, ST, SF, SC

List the 5 heap/vertical development clouds formed in unstable conditions:

CF, CU, TCU, CB, ACC

As an air mass lifted by orographic lift gains altitude, it cools down _____, which can raise the relative humidity to 100% and creates cloud and (under the right conditions), precipitation.

adiabatically

What are the formation factors with orographic lift?

• Slope steepness

• Height of terrain

• Wind direction

• Wind speed

• Humidity

• Stability

What are dissipation requirements for clouds formed by orographic lift and mechanical turbulence?

• Change of air mass

• Change of wind direction/speed

An eddy current is a current of air (or water) _______ to the main current, forming swirls or whirlpools.

moving contrary

What are examples of man-made obstructions that cause mechanical turbulence?

Buildings, obstructions near an airfield

The strength and magnitude of mechanical turbulence depends on:

• Speed of the wind

• Roughness of terrain (or nature of obstruction)

• Stability of air

What is the most important factor in determining the strength and vertical extent of the mechanical turbulence?

Stability of air

What are the formation factors of clouds formed by mechanical turbulence?

• Rough ground

• Strength of winds

• Humidity

• Stability

Vertical motions associated with convergence are typically ____ than the small-scale vertical motions associated with convective processes.

As a result, clouds generated through convergence are typically ______ than convective clouds.

much weaker, less vertically developed

What are the formation factors of clouds formed by convergence?

• Horizontal and vertical extent of it

• Humidity

• Stability

What are dissipation requirements for clouds formed by convergence?

• Change of air mass

• Filling of the low

Clouds formed by orographic lift, mechanical turbulence, and convergence may persist _____.

day or night

What are the formation factors of clouds formed by convection?

• Uneven heating of the Earth’s surface

• Advection of cold air over a warmer surface (i.e. warm water)

What is the dissipation requirement of clouds caused by convection caused by the uneven heating of the Earth’s surface?

When the heating stops

What is the dissipation requirement of clouds caused by convection caused by the advection of cold air over a warmer surface?

The loss of advection or warmer surface

Frontal lifting is when one air mass along a front ______. Frontal lift produces _____.

gets lifted over the other, frontal clouds

Warm fronts produce clouds when ______.

warm air replaces cold air by sliding above it

What type of clouds are created by warm fronts?

AC, AS, CC, CS, CI, CB, NS, ST, SC

With cold fronts, if the warm air is _______ then cumuliform clouds can form.

humid and unstable

The intensity of the cumuliform cloud is closely related to _______. Discounting surface friction, the _____ the cold front, the greater the intensity of the cumuliform cloud that forms.

the speed of the front, faster