Isotherm a line connecting points of equal air temperature. Latent heat energy absorbed or released during a change of state. Millibar standard unit of pressure measurement used by the National Weather Service. Monsoon seasonal reversal of wind direction associated with large continents, especially Asia. Newton a unit of force used in physics.
Polar air masses a cold air mass that forms in a high latitude source region.
Polar front stormy frontal zone separating air masses of polar origin from air masses of tropical origin. Polar front theory theory developed by J. Bjerknes and other Scandinavian meteorologist in which the polar front, separating polar and tropical air masses, gives rise to cyclonic disturbances that intensify and move along the front and pass through a succession of stages. Precipitation Liquid or solid water molecules that fall from the atmosphere and reach the ground. Pressure gradient amount of pressure change occurring over a given distance. Relative humidity ratio of the air's water vapor content to its water vapor capacity.