Air MassUPSC Past papers
• When the air remains over a homogenous area for a sufficiently longer time, it acquires the characteristics of the area. The homogenous regions can be the vast ocean surface or vast plains. The air with distinctive characteristics in terms of temperature and humidity is called an Airmass.
• Warm Air Mass is that whose temperature is greater than the surface temperature of the areas over which it moves. Thus this indicates that the surface underlying the air mass is cold. Due to the presence of cool surface the warm air mass gets cooled from below. The lower layer becomes stable and stops the vertical movement of air. Due to this No adiabatic cooling of air formation of cloud halts precipitation stops creates anti-cyclonic stable conditions Warm air mass can further be divided as continental warm air mass and maritime warm air mass (based on the source of origin whether continent or ocean respectively).
• Cold Air Mass originates in the polar and arctic regions. Temperature and specific humidity is very low. Its temperature is lower than the surface temperature of the areas over which it moves. Thus the air mass is warmed from below and becomes unstable. Due to heating up of air from below, the air rises vertically and because of adiabatic cooling condensation process starts. This will lead to formation of clouds and finally will result in precipitation. But the precipitation will occur only when the air mass is above the warm ocean as it will get the unobstructed supply of moisture whereas if lies above warm continent then leads to clear weather.
• Tropical air masses are warm and polar air masses are cold.