Convection in Clouds

What is convection?

the movement of particles through a substance, transporting their heat energy from hotter areas to cooler areas

Cumulonimbus is an example of?

deep-moist convection

Example of convection through water pot?

When the air bubbles try to escape from the warmer boiling water there is instability/buoyancy so then there is an exchange of heat with the colder air above the pot

What happens when the warm air bubbles escape the boiling water?

STEAM! the air bubbles condense when they touch the colder air (dew point temperature reached); latent heat release heating the ambient air

What are the warm bubbles like?

Positively buoyant due to less dense than the liquid water; unstable: keep lifting and accelerates due to buoyancy

How does Earth’s surface act similar to boiling water?

Positive sensible heat flux upwards that heats the flow above the surface

Then what occurs that produces “warm bubbles”?

turbulent nature of the flow makes the flow unevenly heated producing these “bubbles”

What happens to this air?

these warm bubbles (thermals!) are buoyant and unstable, so they ascend to higher

When the thermals expand what occurs to its temperature?

The temperature will drop due to the expansion

What will then happen to some of the cooled thermals?

if “lucky” thermals, which is moist enough, can reach saturation and become clouds

Severe heat exchange processes driven by instability will cause what?

dry convection (within the boundary layer) and moist convection (clouds)

What do these turbulent, chaotic, widespread events occur?

Surround us everywhere in daytime, clear-sky boundary layer

How are sky conditions described?

cloud coverage is divided into eighths or tenths and each amount associated with term such as “scattered clouds or “overcast”

Satellite Orbits Where: geostationary or geosynchronous?

orbit at ~36,000km above equator and travels at Earth’s angular velocity

Satellite Orbits Where: polar-orbiting?

Orbit typically at ~ 400 to 900km altitude; closer to Earth Surface and higher spatial resolution imagery

What does a midlatitude cyclone visible image look like? (satellite view)

thick clouds reflect light more and so appear white

What does a infrared image of a midlatitude cyclone look like? (satellite view)

high cloud tops are cold and so emit less IR and appear white; low cloud tops are warm and so emit more IR and so appear grey