Chapter 4 Moisture and Atmospheric Stability

is the amount of energy required to raise the temperature of 1 gram of water 1 degree Celcius, 1.8 degree F.

The process of converting a liquid to a gas (vapor).

The reverse process, occurs when water vapor changes to the liquid state.  During condensation, water vapor molecules release energy (latent heat of condensation) in an amount equivalent to what was absorbed during evaporation.

Is the conversion of a solid directly to gas, without passing through the liquid state.

The conversion of a vapor directly to a solid.

Used to describe the amount of water vapor in the air.

As the part of the total atmospheric pressure attributable to its water vapor content.

Is the ratio of the air's actual water vapor content compared with the amount of water vapor required for saturation at that temperature (and pressure).

Is the temperature at which water vapor begins to condense.

The altitude at which a parcel of air reaches  saturation and cloud formation begins.

When a parcel of air ascends above the lifting condensation level, the rate at which it cools is reduced.

Produces rising thermals

If the parcel of air is cooler than the surrounding environment, it will be more dense; and if allowed to do so, it will sink to its original position.  Resists vertical movement

If, however, our imaginary rising parcel of air is warmer and hence less dense than the surrounding air, it will continue to rise until it reaches an altitude where its temperature equals that of its surroundings.

Prevails when the environmental lapse rate is less than the wet adiabatic rate.

When the environmental lapse rate is greater than the dry adiabatic rate.

Prevails when moist air has an environmental lapse rate between the dry and wet adiabatic rates (between about 5° and 10°C per 1000 meters).

The altitude at which air rises because of its own buoyancy.

Is a layer of the atmosphere in which temperature increases with with altitude, rather than the more common condition of decreasing with altitude.

A smaller amount of groundwater is taken up by plants, which release it into the atmosphere.

Heat energy was neither added to nor subtracted

The surrounding air infiltrates a rising or descending column of air.

Occurs when elevated terrains, such as mountains, act as barriers to the flow of air.

Warm and cold air masses often collide, producing boundaries called fronts.  Rather than mixing, the cooler, denser air acts as a barrier over which the warmer, less dense air rises.

When the wind pattern near Earth's surface is such that more air is entering an area than is leaving-a phenomenon called convergence-lifting occurs

Rising parcels of warmer air.

When a parcel of air is forced to rise, its temperature will decrease because of expansion.