In the thin envelope of air that surrounds the earth, gravity compresses the air molecules as closely as possible to the surface. As a result, half the weight of the atmosphere is contained within only about four miles. Thus the pressure exerted by the air drops very rapidly with elevation. Any bubble of rising air must expand to come to equilibrium with its peers at the new level; and work is required for the expansion.

This manifests as a drop in temperature at the rapid rate of 1 degree Celsius per 100 meters. This rapid cooling of ascending air results in humidification of the rising air. When saturation is reached, tiny airborne particles of dust and salt become centers on which water molecules stick, and grow, becoming cloud droplets. This is how 99 percent of all clouds are formed. With the growth of cloud particles, raindrops and snowflakes are produced. Up leads to psychological down.

Conversely, downward motion in the atmosphere leads to compressional warming which leads to drying which leads to clear skies. Air motion from the continent to the coast is sinking air.

Down leads to psychological up. Confusing, isn't it?

See Under-the-Weather Man for more on the up-down effect.