The pressure gradient is the force that is produced due to the rotation of earth pressure cells that creates lighter air to move upwards and heavier to move downwards due to the difference in densities of air.
As the air above consists of lighter elements the oceanic air mostly consist of diatomic molecules of oxygen and nitrogen thus containing a large amount of water vapor, all these molecules have a mass that are pulled down by the gravity and this pull of gravity on columns of gas applies a force what we see an atmospheric pressure.
The gas particles and molecules of heavy and denser matter get stuck at the ground, similarly, as the air cools is descends and warm air rises. Thus upwards and downward motion of air causes convergence and divergence of molecules.
Permeability id a scientific index of the soil to have air and water pass through the soil pore and spaces. As clay soils have a fine texture, with loamy soils moderately textured and sandy soils coarsely textured thus permeability changes from slow to rapid.
As sandy soil is highly permeable i.e 5.0 cm per hour and clay soils having the least i.e 0.05 permeability. Loamy soil is composed of sand, silt, and a smaller amount of clay.
From an agricultural perspective, the soil permeability depends upon the percentage of the see-page and the chemical makeup of the soil. Thus crops can grow more easily this type of soil as the particle size is minute and fine.
