Topics: Air mass, Warm front, Meteorology Pages: 7 (2122 words) Published: December 6, 2012
Air Mass
Q1 A Air Mass is an extremely large body of air whose properties of temperature and moisture content (humidity), at any given altitude, are fairly similar in any horizontal direction. * can cover hundreds of thousands of square miles.

there can be small variations

An air mass is a large body of air that have similar characteristics, such as pressure, temperature, and moisture. What determines its characteristics is the source region. The source region is the surface over which it is formed. For example, if an air mass formed over an ocean near the equator, it would be called a mT. m stands for maritime (ocean) and T stands for tropical (near the equator/hot). Hope this helped!

BThere's actually six which affect Ireland.

There are four main types of air mass.

Tropical continental (Tc)
Tropical maritime (Tm)
Polar continental (Pc)
Polar maritime (Pm)

And two further sub-divisions.

Arctic maritime (Am)
Returning polar maritime (rPm)

C Home Secondary Key Stage 4 Air
Key Stage 4 - Air|
Air masses and fronts1. Introduction
    1.1 Definition
    1.2 Source of an air mass
    1.3 Air-mass modification2. Air-mass types
    2.1 Tropical continental
    2.2 Polar continental
    2.3 Tropical maritime
    2.4 Polar maritime
    2.5 Arctic maritime
    2.6 Returning polar maritime3. Between the air masses
    3.1 Historical introduction
    3.2 Fronts
    3.3 Models of mid-latitude depressions
    3.4 The passage of a mature depression across the United Kingdom 
4. Questions 1. Introduction
1.1 DefinitionAir masses are parcels of air that bring distinctive weather features to the country. An air mass is a body or 'mass'of air in which the horizontal gradients or changes in temperature and humidity are relatively slight. That is to say that the air making up the mass is very uniform in temperature and humidity.An air mass is separated from an adjacent body of air by a transition that may be more sharply defined. This transition zone or boundary is called a front. An air mass may cover several millions of square kilometres and extend vertically throughout the troposphere.1.2 Source of an air massThe temperature of an air mass will depend largely on its point of origin, and its subsequent journey over the land or sea. This might lead to warming or cooling by the prolonged contact with a warm or cool surface. The processes that warm or cool the air mass take place only slowly, for example it may take a week or more for an air mass to warm up by 10 °C right through the troposphere. For this to take place, an air mass must lie virtually in a stagnant state over the influencing region. Hence, those parts of the Earth's surface where air masses can stagnate and gradually attain the properties of the underlying surface are called source regions.The main source regions are the high pressure belts in the subtropics, which produce tropical air masses, and around the poles, that are the source of polar air masses. | | | |

Fig 1: Polar and tropical source regions. 
The blue and red arrows show the polar and tropical regions respectively.1.3 Air-mass modificationAs we have seen, it is in the source regions that the air mass acquires distinctive properties that are the characteristics of the underlying surface. The air mass may be cool or warm, or dry or moist. The stability of the air within the mass can also be deducted. Tropical air is unstable because it is heated from below, while polar air is stable because it is cooled from below.As an air mass moves away from its source region towards the British Isles, the air is further modified due to variations in the type or nature of the surface over which it passes. Two processes act independently, or together, to modify an air mass.An air mass that has a maritime track, i.e. a track predominantly over the sea, will increase its moisture content, particularly in its lower layers. This happens through evaporation of water from the sea surface....
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