why do the base of the clouds get flat?

Answer 1

do they?

Answer 2

There are a couple reasons.

One time you will see that is in the late afternoons and evenings when the sun's heating is causing/has caused the air near the ground to rise. As it does, it reaches a level where it has exanded and cooled to the dewpoint. (Not ALL the air near the ground can rise, but pockets here and there will.)

The low-level air may have a temperature of 87F with a dewpoint of 65F. Therefore, when it rises to an altitude that makes it expand and cool to 65F, condensation begins. Clouds. Usually, but not always, the temperatures near the ground, and the dewpoints, will be pretty uniform across a broad area, and so all the clouds will also have bases at pretty much the same altitude across broad areas. That's right where the humidity reaches 100%. The less the difference between the temp and the dewpoint, the lower the cloud bases, because then that air doesn't have to rise so far to cool to the dewpoint.

Other times, a layer of saturated air (filled with clouds) slides across the top of a stable near-ground layer of air. The winds generally blow more slowly at lower altitudes because of the friction of the earth (trees, buildings, everything...), so it's not at all uncommon for a layer of clouds to overrun that layer.

*edit* Bonus info! LOL... The rate at which air cools as it rises while it remains unsaturated is called the dry adiabatic lapse rate. It is approximately 6 degrees per 1000 feet. (It is exactly 9.8C/Km.) What does that tell you? It tells you that if the cloud bases are at 4000 feet above ground, the difference between the temp and the dewpoint is about 24 degrees F. Or that if the sky is clear, but storms are expected, and the difference is only 6 degrees, cloud bases will be at a mere 1000 feet once convection initiates. That can be a prescription for trouble.

Answer 3

Basically its where the temperature is cool enough to support condensation to form a cloud without being saturated enough to form precipitation (i.e., rain, snow, hail).

This assumes that there is no updrafts or other atmospheric mixing taking place.

Answer 4

bob is right, but keep in mind that his numbers are for a standard sky with surface pressure at 29.94 inches and calm winds. Keep in mind that there is always some kind of monkey in the wrench. (mixing, inversions. etc.)

Answer 5

How do people find time to think of something like this, do they just sit in the grass and look at the sky all day?

Answer 6

wind currents and thermals and pressure

Answer 7

i did'nt know they get flat

Answer 8

wind currents under them probably....

Answer 9

domi is right, i didn't see that.