M - O

M

Magnetosphere The region around the earth in which the earth's magnetic field plays a dominant part in controlling the physical processes that take place.

Maritime air mass An air mass that originates over the ocean. These air masses are relatively humid.

Mesoscale The scale of meteorological phenomena that ranges in size from a few km to about 100 km. It includes local winds, thunderstorms, and tornadoes.

Mesosphere The atmospheric layer between the stratosphere and the thermosphere. Located at an average elevation between 50 and 80 km above the earth's surface.

Meteorology The study of the atmosphere and atmospheric phenomena as well as the atmosphere's interaction with the earth's surface, oceans, and life in general.

Microclimate The climate structure of the air space near the surface of the earth.

Microscale The smallest scale of atmospheric motions.

Millibar(mb) A unit for expressing atmospheric pressure. Sea level pressure is normally close to 1013 mb.

Mirage A refraction phenomenon that makes an object appear to be displaced from its true position. When an object appears higher than it actually is, it is called a superior image. When an object appears lower than it actually is, it is an inferior mirage.

Mist Very thin fog in which visibility is greater than 1.0 km (0.62 mi). 
Modelling It is the transformation of structural and functional behaviour of the system in to graphic, mathematical and/statistical formulation.

Moist adiabatic rate The rate of change of temperature in a rising or descending saturated air parcel. The rate of cooling or warming varies but a common value of 6ºC per 1000 m (3.3ºF per 1000 ft) is used.

Molecular viscosity The small-scale internal fluid friction that is due to the random motion of the molecules within a smooth-flowing fluid, such as air.

Mountain and valley breeze A local wind system of a mountain valley that blows downhill (mountain breeze) at night and uphill (valley breeze) during the day. 

N

Nutrient Budget The measure of the input and outflow of elements through the various components of ecosystem.