AIR MASS AND ITS TYPES AND FRONT AND DIFFERENT KINDS IF FRONTS
- 1. Air mass & Fronts ➢Definitions and Properties ➢Types and classifications ➢Interactions ➢ Significance
- 2. Air mass- Introduction These are extensive portion of atmosphere which adapt properties like temperature, moisture content etc. According to the type of region present below them when they stay for an adequate amount of time over the source region. These regions from where the air mass adapt these properties are called source regions. They show horizontal and vertical homogeneity. Air masses can extend from hundreds of thousands to millions of square kilometers. Air masses can extend from surface level to the end of troposphere & at different latitudes.
- 3. Origin and classification- Most notable centres for creation of airmass are >High pressure areas at the outer limits of hadley cell >high pressure regions over poleward continental margins Note- low pressure zones are not suitable for origin of air masses Air masses are classified considering two factors- >latitudinal position >underlying surface Latitudinal position like arctic and antarctic, polar, tropical, equatorial are considered. Continent and oceans are the main two types of underlying surface in consideration.
- 4. Types of air masses- Considering the two main classifying factors air masses are the following types- >maritime equatorial(mE) >continental tropical(cT) >maritime tropical(mT) >maritime polar(mP) >continental polar(cP) >continental arctic(cA) >continental antarctic(cAA)
- 5. Air masses present in different geographical locations-
- 6. Modification of air mass- The modification or changes happens to the air mass when they move away from its source region. This modification can happen in two forms- I. Thermodynamic modification In thermodynamic, the temperature change happens at low layer through transfer of heat from new source region. Here the degree of modification in air mass is controlled by factors like nature of underlying surface, path of movement, duration of travel and the addition of moisture. II. Dynamic modification In dynamic type, mainly pressure changes happen in the air mass. Here factors involved like turbulence, high level convergence, divergence, turbulent mixing etc.
- 7. Zenith angle and air mass- These two are related by- Air mass = Here, is the zenith angle Note- zenith angle is angle formed between the two positional path of sun radiation when passing through air mass measuring from a fixed point on surface. Here zenith position is exactly above the surface point. And another position of sun is other than zenith position.
- 8. Fronts- Fronts are natural phenomenon related to air masses. Fronts are created due to interaction between two or more air masses. We can say fronts are the areas of intersection between two air masses. The frontal regions are areas of disturbances and high activities on atmospheric level. Frontogenesis-creation of front Frontolysis-destruction of front
- 9. Classification of Fronts- According to the types and movement of air masses fronts are classified into majorly 4 types- I.Cold front II.Warm front III.Occluded front IV.Stationary front
- 10. I. Cold front- Cold fronts are created when moving cold air mass comes towards a stagnant warm air mass and meet. Here a frontal slope is created between them which is steeper in this type. Here the slope ratio is 1:50 to 1:100. Due to frontal action the low dense air of warm air mass is lifted over and precipitated. Here cumulonimbus clouds/vertical clouds are formed. These clouds are responsible for heavy rain with thunderstorm and lightning in narrow region for a short period of time.
- 11. II. Warm Front- Warm fronts are created when a moving warm air mass meets a stagnant cold air mass. Here the frontal slope created is not steeper like cold front, rather a smooth slope here. Here slope ratio is 1:100 to 1:400. Warm air rises up gently over the warm front with slow precipitation. Clouds nimbostratus, altostratus, cirrostratus, cirrus clouds are formed. These cloud make low to moderate rain over a wide region for long period of time causing warm humid climate.
- 12. III. Occluded front- This type of front is created with involvement of 3 air masses. Cold front completely lifts off the warm front cutting of the warm air mass touching the surface. Two types of occlusion occurs like cold front occlusion and warm front occlusion. Here nimbostratus, cumulostratus clouds are formed at low pressure regions with patchy rain.
- 14. IV. Stationary Front- This front is created when two air masses of equal strength and momentum converge towards each other. No ascending of air happens here. The front does not move forward or backward like the name suggests. Here altocumulus clouds are formed on cold side causing gentle wind with rain. Here temperature remains constant.
- 16. Frontal zones- There are three major frontal zones- I. Arctic frontal zone(convergence of continental and maritime polar air masses) II. Polar frontal zone(convergence of continental polar and maritime tropical airmasses) III. Intertropical frontal zone(formed due to convergence of north east and south west trade wind from north and south hemisphere n equatorial region
- 17. Significance of Air mass & Fronts- Both air mass and fronts are best area to study different properties of air like temperature, pressure, humidity etc. correlating with the source region of different latitude, altitude, longitude and other factors. They help in studying current climatic condition, other phenomena like cyclones tornado and also help in predicting weather condition in different area according to their movement. Presented by SATYAJIT SAHOO +3 3rd year Roll no-UNGEO21004 THANK YOU