But convection currents are ultimately at the mercy of temperature differences because these are what create pressure differences in the first place. The pressure difference between two locations is called a pressure gradient, and the force that actually moves air as wind is called the pressure gradient force.
oÂ·nus. n. 1. A difficult or disagreeable responsibility or necessity; a burden or obligation. 2. Responsibility for an error or fault; blame: Each side wants to avoid the onus of having started the disagreement. 3.
tonus. A state of partial contraction present in a muscle in its passive state as, for example, when the eye is in the physiological position of rest. Syn. muscle tone. See resting state of accommodation; physiological position of rest; tonic vergence.