Skip to main content

Jet Streams

Q.Write short note on Rossby waves and Jet stream. (12/11)
Jet Streams are fast flowing narrow stream of Geostrophic westerly winds found in upper troposphere near tropopause which encircles globe at respective latitudes.
         Peterson has defined jet streams as thermal winds produced by great temperature contrast found between meridional cells which produces intense pressure gradient.
CHARACTERISTICS
  • Genesis:They are product of high pressure gradient, strong coriolis and negligible friction which is ideal for geostrophy.
  • Speed: varies from 120 Km/hr to 900 Km/hr
  • Seasonal Migration: During winter, they are poleward while in summer they shift equatorward.This is associated directly to the shifting of meridional cells with seasons.
  • Rossby Waves: Associated with polar front jet stream.They follow meandering path which appears like waves with crest and trough.Crest and trough have north-south alignment perpendicular to the path of jet stream.This meandering jet streams are also referred as Rossby waves. This meandering is due to cold air mass from north and warm air from south invade in each others territory distorting the path of polar front jet stream.
  • Crest and trough: Associated with subtropical jet stream.Jet streams near equator  tends to form crest and trough which is acceleration toward ground or moving away from it.These are formed due to contrast in pressure gradients existing between ocean and continents and angular momentum conservation principle.As it move towards,continent, gradient intensifies and it tends to make trough while moving from land to ocean, it tends to form crest.
TYPES
1.Subtropical Jet Stream
  • It is formed between hadley cell and Ferrel cell due to temperature contrast resulting intense pressure gradient.
  • Associated with crest and trough formation.Crest is associated with cyclogenesis and low pressure condition while trough is associated with subsidence of air and anti-cyclogenesis conditions.Formation of thar desert is also due to sub-tropical jet stream forming trough there.
  • Steers Western disturbances toward india
  • Associated with retreat of monsoon: retreat of monsoon occurs as it appears over norther part of india around gangetic plains.
2.Polar Front Jet Stream
  • This was discovered by Rossby.
  • It is formed between polar cell and ferrel cell where temperature.
  • Speed varies between 90 -120 Km/hr
  • It is characterized by rossby wave formation and follows index cycle.
  • Index cycle describes various stages where no-meandering stream transform into rossby wave and again dissipates back into non-meandering jet stream.
  • Index cycle goes through 4 stages
  1. Incipient stage: non-meandering stage
  2. Juvenile stage: development of small wave due to warm  air from south and cold air from polar region stats to invade each other
  3. Mature stage: full fledged rossby wave due to further of invasion of cold and warm air in each other’s territory
  4. Dissipation stage: cold air and warm air enter each other's territory and mix up which results in vanishing of rossby wave.
  • Telepathic influence on Temperate Cyclone formation and movement.
rossbyWave.jpg




 3.Tropical Easterlies Jet
  • Originates due to excessive heating of tibetan plateau.Rising air flows outward after reaching higher troposphere.One stream flow towards gangetic plain and form Tropical easterlies jet
  • It lies over gangetic plain and oscillates between shivalik and vindhyas.
  • It is related to the onset of monsoon in indian subcontinent.
  • It also affect monsoonal rainfall over gangetic plain by determining the monsoonal trough over gangetic plain.
  • It also steers tropical cyclones into India.
     
4.Findlater Jet
  • Formed between Warm Mozambique air mass  & African Highland cold air mass due to thermal contrast.
  • It bifurcates due to african highland and right channel directs southwest monsoon into india

5.Polar Night Jet

Labels:

Comments

Post a Comment

Popular posts from this blog

DAVIES,PENCK & KING

Geographical Cycle of Davies William Morris Davies was an american geographer who gave first general theory on landform development.. Davis' most influential scientific contribution was the "geographical cycle",  which he defined in an article,’ The Rivers and Valleys of Pennsylvania ,’ published at the end of 19th century. According to him, uplifted landmass undergoes sequential development or erosion till base level in various stages.This sequential development referred as cycle of erosion. FUNDAMENTAL PRINCIPLES 1.Cyclic nature of landform evolution. 2 Uniformitarianism:The same physical processes and laws that operate today, operated throughout geologic time, although not necessarily always with the same intensity as now BASIC POSTULATES Upliftment takes place on featureless plain which he modified 10 yrs later to accept it can occur from geosyncline. Upliftment on geological timescale is sudden.In later works, he accepted it to be episodic. ...
Post a Comment
Read more

Rimland Theory

It was given by John Spykman which was published posthumously. It was a reaction to Mackinder’s Heartland Theory.He also believed in historical struggle between land and sea powers.But, his view were similar to Alfred Mahan’s idea of supremacy of sea power. CRITICISM OF HEARTLAND 1.Climatic hazards and physiographic difficulties 2.Non-ecumen region devoid of most important human resource.Thus,Resources remain unutilized. 4.Accessible from west and south West and merely few hours distance from N America RIMLAND It was similar to Mackinder’s inner crescent which comprised 3 sections 1.European Coast 2.Arabian middle east desert land 3.Asiatic monsoon land ADVANTAGES OF RIMLAND 1.¾ th of population and most of world resources like coal,petroleum,iron ore,etc. 2.Largest agricultural tract. 3.Suitable climate. 4.Variety of human race. According to him,those who control rimland,rules eurasia.And who rules eurasia controls destinies of world. APP...
2 comments
Read more

Rene Descartes: A Critique

Introduction René Descartes (1596-1650) was a French philosopher, mathematician, and scientist who is considered one of the founders of modern Western philosophy. He is known for his contributions to analytic geometry, his development of the scientific method, and his famous philosophical statement "Cogito, ergo sum" ("I think, therefore I am"). Descartes is also known for his works on metaphysics, epistemology, and the philosophy of mind. Descartes' ideas had a significant impact on the development of Western philosophy and science. His emphasis on reason and mathematical reasoning as a tool for discovering truth has been influential in the development of the scientific method. Additionally, his ideas on the separation of mind and body and the nature of reality have continued to be influential in modern philosophy. Descartes' works include "Meditations on First Philosophy," "Discourse on the Method," and "Principles of P...
Post a Comment
Read more