Fronts

Fronts- types and frontal zones

1. FRONTS Simran Sehrawat 2145520009 M.A. I Semester Academic Session: 2018-2019

2. FRONTS When two contrasting air masses meet, they form a front , which is a boundary that separates two air masses. The sloping boundary between two contrasting air masses of contrasting characteristics in terms of temperature, velocity, humidity, density etc. is normally called FRONT .

3. FRONTOGENESIS- The process associated with the creation of new fronts or regeneration of old and decaying fronts already in existence is called frontogenesis. FRONTOLYSIS- The process of destruction or dying of old fronts is called frontolysis.

4. CLASSIFICATION Fronts are classified into four principal types on the basis of their different characteristic features : Cold Front Warm Front Occluded Front Stationary Front

5. FRONT SYMBOLS

6. COLD FRONT Cold front is advancing ,in which cold air becomes active and aggressive and invades the warm air territory and being denser remains at the ground surface and forcibly uplifts the warm and light air. In simple terms, cold air mass replaces a warm air mass Slope- 1:50 to 1:100 Cold front is much steeper than the warm front

7. Associated with bad weather – Thick clouds Heavy downpour Thunderstorms Lightning Temperature decreases with the arrival of cold front, sky becomes overcast with cumulo-nimbus clouds, heavy precipitation occurs but for short duration. After the passage of cold front, clouds disappears, precipitation terminates and weather becomes clear.

8. WARM FRONT In warm front, warm and light air becomes active and aggressive and rises slowly over cold and dense air. The slope of the front is gradual- 1:100 to 1:400 As the front approaches the clouds lower and thickens progressively to cirrostratus, altostratus, and nimbostratus.

9. Precipitation- light to moderately heavy and continuous, extending over a wide zone. Gradual increase in temperature and weather tends to be warm and humid

10. OCCLUDED FRONT Occluded front is formed when cold front overtakes warm front and warm air is completely displaced from the ground surface. There are two ways in which an occlusion may form – Cold-front occlusion - when the air behind the cold front is normally colder than that ahead of the warm front, as occlusion develops the cold front overtakes warm front.

11. Warm-front occlusion - where the air behind the cold front is warmer than that ahead of the warm front, the retreating (cool) air overtakes the advancing (cold) air, producing a warm-front occlusion

12. STATIONARY FRONT Stationary front is formed when two contrasting air masses converge in such a way that they become parallel to each other and there is no ascent of air. This front doesn’t move either forward or backward i.e. two air masses are “standoff” Temperature remains constant and winds are gentle Several days of altocumulus clouds and likely precipitation on cold side

13. FRONTAL ZONES There are 3 principal frontal zones on the earth’s surface Arctic Frontal Zone Polar Frontal Zone Inter-Tropical Frontal Zone

14. ARCTIC FRONTAL ZONE Created in the arctic areas due to convergence of continental and maritime polar air masses Theses fronts are not very strong and active(because of less temp. contrast b/w two air masses) Active fronts are formed when relatively warm polar maritime air mass meets extremely cold arctic air mass These develops along the arctic coasts of Eurasia and North America

15. POLAR FRONTAL ZONE Formed in middle latitudes (in both hemispheres) because of convergence of polar continental air mass and tropical maritime air mass They are more active in winter seasons while weakened during summer season (because temp. contrast is more propounded) The temperate cyclones produced along polar front travel from west to east(because the temp. contrast b/w two air masses decrease to minimum)

16. INTERTROPICAL FRONTAL ZONE Acc. To some meteorologists tropical fronts is formed near the equator due to convergence of north east and south east trade winds However, there is no temperature contrast between these two air masses(trades) of similar origin and some properties

17. REFERENCES Singh, Savindra. (2016). Climatology, Allahabad, U.P. : Pravalika Publications Critchfield, Howard. J. (2015) General Climatology, (4). Noida, U.P. : Pearson Indian Education Services Pvt. Ltd. https:// www.pmfias.com/fronts-frontogenesis-stationary-front-cold-front-warm-front-occluded-front/ https ://blog.weatherops.com/there-are-four-basic-types-of-fronts-can-you-name-them Images from net surfing