gradient of refraction

the vertical temperature-gradient at considerable altitudes as affected by fenemena of refraction. initial gradient, the small gradient of pre ure of the air at about seaclevel where the slight variations of pre ure’ due to differences of density of the air, the tides, etc., snttiate or give rise to the winds which cause the larger (observd) barometric gradients. neutral gradient of pre ure, a vertical pre ur-gradient whose maintain ance keeps the atmosfere neutral or in dynamic equalibrium. vertical gradient, the gradient according to vertical height above the earth; the rate at which any atmosferic condition, as temperature or pre ure, ete, varies with the altitude.