The tendency of the atmosphere to resist or enhance vertical motion is termed stability. It is related to bothwind speed and the change of air temperature with height (lapse rate). For our purpose, we may use the lapserate alone as an indicator of the stability condition of the atmosphere.There are three stability categories. When the atmosphere is classified as unstable, mechanical turbulence isenhanced by the thermal structured. A neutral atmosphere is one in which the thermal structure neither enhancenor resists mechanical turbulence. When the thermal structure inhibits mechanical turbulence, the atmosphere issaid to stable. Cyclones are associated with unstable air. Anticyclones are associated with stable ai