Find out the concept given in the jet stream theory and affects of jet stream on the indian monsoon which is very useful for the competitive examinations like upscprelims, ssc, state services. It is characterized by wind circulation at lower level at 850 hpa as southwesterly jet and at upper level at 200 hpa as easterly jet and produced wide spread rainfall over vast land area of indian continent in four months starting from june and ending in. Both the northern and southern hemispheres have jet streams, although the jet streams in the north are more forceful due greater temperature gradients. A study of south asian monsoon convection and tropical upper easterly jet during northern summer 1991 author. Geography influence of jet streams on the south west monsoon. Therefore, its response to climate change is of great concern to climate scientists. Jan 21, 2016 indian monsoon mechanism modern theory. Above the lowlevel westerlies, and distinct from the harmattan easterlies and the tropical easterly jet, is the african easterly jet maximum at 600 mb and 8n. The monsoon approaches the indian landmass in two branches. This strong flow of air that develops in the upper atmosphere during the asian monsoon is centred on 15n, 5080e and extends from southeast asia to africa. Decreasing trend in the strength of tropical easterly jet during the asian summer monsoon season and the number of tropical cyclonic systems over bay of bengal. Pdf weakening trend of the tropical easterly jet stream. African easterly wave variability and its relationship to.
A careful study of the easterly jet suggests that its core is located at higher altitude than the core of the westerly jet in extratropical altitudes as such the level of maximum wind in the easterly jet is about km while the core of westerly jet is about 9km. If one hemisphere of a planet like earth has summer, then the other hemisphere will have winter. This easterly jet stream is held responsible for the burst of the monsoon. Monsoon refers to those seasonal winds which changes their direction twice in a year with the change in season. The north east monsoon winter monsoon is related to the subtropical westerly jet stream which blows between 20 degree and 35 degree. Dec 15, 2016 the foregoing holds on individual days and climatically during the monsoon season as a whole.
The southwest monsoon season jun sep part 2 civilsdaily. This indicates that the easterly jet is intensified in an active monsoon situation. It may be pointed out that the tropical easterly jet stream first develops in longitudes lying east of india, and then extents westwards across india and the arabian sea to eastern africa. Since an easterly jet stream is observed only over southern asia and africa, but not over the pacific and atlantic oceans, it is suggested that the current originates in connection with the largescale arrangement of land masses and oceans, and with. Because the low level monsoon circulation is subject to distortion by the small scale. Monsoons are peculiar to indian subcontinent, south east asia, parts of central western africa etc. Atmosphere free fulltext investigating west african monsoon. It is also a major reason why there are no cyclones during monsoon because the presence of an easterly jet over the indian landmass in the upper troposphere prevents vertical circulation of air, which is a precondition for formation of cyclones.
In summer, the subtropical westerly jet stream moves north of the himalayas with the apparent movement of the sun. Jun 16, 2018 the west african summer monsoon wasm rainfall is of significant socioeconomic importance. Tropical easterly jet tej there are major high velocity winds in the lower troposphere called lowlevel jets lljs. Chart and diagram slides for powerpoint beautifully designed chart and diagram s for powerpoint with visually stunning graphics and animation effects. The tropical easterly jet is the meteorological term referring to an upper level easterly wind that starts in late june and continues until early september. In the tropics, the most prominent of these are the somali jet and the african easterly jet. The jet s maximum wind speeds are at a height of 3 kilometres 1. The rain is primarily due to coalescence of droplets, with most of the clouds located below 3,500 metres 11,500 feet. Permanent high pressure cell in the south of the indian ocean. Krishna in 1952 and aroused considerable interest among tropical meteorologists. C10 jet streams for upsc iasimpact of jet streams on weather. The easterly jet stream steers the tropical depressions into india. Krishnamurti in the book monsoon models offers a detailed explanation. The narrow belt of strong easterly winds is observed between 100 and 200 hpa over southern periphery of india through out the southwest monsoon season june through september.
The monsoon is a double system of seasonal winds they flow from sea to land during the summer and from land to sea during winter. Fluctuations of tropical easterly jet during contrasting monsoons. Mar 16, 2015 jet stream is a manifestation of wind flow in planets during winter seasons. A careful study of the jets would suggest that the core of the easterly jet is at. The centers of action, air masses involves, and the mechanism of precipitation of indian monsoon are altogether different from other monsoon. This jet is a prominent feature of the upper air circulation during the indian summer monsoon season june september. This strong flow of air that develops in the upper atmosphere during the asian monsoon is centred on 15n, 5080e and extends from southeast. Jet stream theory is the latest theory regarding the origin of the monsoons and has earned worldwide acceptance from the meteorologists. Above the lowlevel westerlies, and distinct from the harmattan easterlies and the tropical easterly jet, is the african easterly jet maximum at 600 mb and n. Ensemblebased cmip5 simulations of west african summer. The elements of the monsoon system include pressure of the monsoon trough, pressure of the mascarene high, crossequatorial lowlevel jet, tibetan high, tropical easterly jet, monsoon cloud cover, monsoon rainfall, dry static stability of the lower troposphere, and.
Role of indian ocean warming 1679 monsoon season might be responsible for the tej weakening24. Effect of changing tropical easterly jet, low level jet. Stratospheric easterly winds penetrate downwards into the northern branch of the tej. Some scholars tend to treat the monsoon winds as land and sea breeze on a large scale.
The wam system consists of many atmospheric features such as monsoon flow, african easterly jet aej, tropical easterly jet tej, african easterly waves aews, and mesoscale convective systems mcss interacting in a complex way to provide the summer monsoon rainfall. The southwest monsoon dominates the weather, and clouds and rain abound. Possible changes in the characteristics of indian summer. Ism is characterized by few important features in the troposphere such as seasonal wind reversal in the lower level, low level jet stream and the tropical easterly jet stream tej in the upper level.
Climate of india iasmania civil services preparation. Citeseerx generation of the african easterly jet and its. Note tropical easterly jet stream which is associated closely with the burst of monsoon. The eastern jet becomes powerful and is stationed at 15 n latitude. Indian monsoons role of tropical easterly jet tej african. The tropical easterly jet tej is a zonal wind generally located around 510 n. Koteswaram,meteorological office, calcutta airport manuscript received february 2, 1957 abstract it is shown that in summer an easterly jet stream overlies southern asia in the high tropo. The tropical easterly jet stream tej, whose existence was established by koteswaram 1958, the lowlevel jet stream llj discovered by joseph and raman 1966 and findlater 1969, and the tibetan anticyclone north of the tej are the important components of the asian summer monsoon system and parts of the monsoon hadley cell krishnamurti and bhalme 1976. Sw monsoon winds bring heavy rainfall to most parts of the country. An easterly jet stream, called the subtropical easterly jet stream blows over peninsular india, approximately over 14n during the summer months. Fluctuations of tropical easterly jet during contrasting. Indian monsoons intertropical convergence zoneindian monsoon mechanismhow jet streams affect indian monsoons. Download now this volume presents a survey of our state of knowledge of the physical and dynamical processes involved in the asian monsoon. Subtropical jet stream stj the subtropical jet stream is produced by the earths rotation coriolis.
Longterm trends and their features during active and break monsoon phases. Decreasing trend in the strength of tropical easterly jet. This paper, however, assesses the role of an upper troposphere synoptic feature of importance in modulating surface rainfall over sudan in the eastern sahel. An examination of analyses and model simulations is used to show that the african easterly jet forms over west africa in summer as a result of strong meridional soil moisture gradients. Koteshwaram, the disappearance of this jet from the south of the himalayas paves the way for the burst of southwest monsoon along the coast of kerala. Jetstreams polar, subtropical, tropical easterly, somali. Monsoons in india, read more about the monsoon winds of india. Academics in indian summer monsoon rainfall analysis with. The strongest development of the jet is at about 15 km above the earths.
Go to previous content download this content share this content add this content to favorites go to next content. Maps south asia monsoon diercke international atlas. Assessing the capabilities of three regional climate models. The tropical easterly jet hereafter called tej in the upper troposphere is the return flow of the summer monsoon thermally direct circulation in the tropical asian region 1030n, 40120e. Citeseerx document details isaac councill, lee giles, pradeep teregowda. The tropical easterly jet ensures a shifting of the southwest monsoon flow in the shallow areas of low pressure. Using longterm observational datasets, abish et al. These upper level easterly jet stream create flow of air on the southern side of tibetan plateau that reaches down to low levels over northern most india. Recent work on sahelian rainfall anomalies has concentrated on modelling of both ocean heat anomaly forcing of regional lowmid troposphere circulation and land surface forcing of precipitation processes. When it is strong, it opposes the spread of the south west monsoon and when it is weak, it allows the spread of south west monsoon. This results in more active southwest monsoon and heavy rainfall is caused.
Aug 04, 2017 easterly jet stream and tropical cyclones. The tropical cyclones were discussed in detail in the discussion on summer season. The southwest monsoon season jun sep part 1 civilsdaily. Before the monsoon onset, the upper air jet stream is westerly over india but as the monsoon onsets, it changes its dire. This is known as tropical easterly jet tej first observed by koteswaram. Intense lowpressure formation over the tibetan plateau. This easterly jet stream is held responsible for the burst of the monsoon in india. Indian monsoon in india physical geographyupscias exam. A study of south asian monsoon convection and tropical upper. It is the main causative factor for determining the vigour of the summer monsoon in india.
African easterly jet tropical easterly jet intertropical convergence zone itcz. The monsoon system of the indian subcontinent differs considerably from that of the rest asia. Tropical easterly jet stream this jet stream is oriented along the kolkatabangalore axis in that direction. In west africa, two lowlevel westerly flow regimes are important for the.
Jan 21, 2016 this jet descends over the indian ocean near madagascar and intensifies its high pressure cell so as to move as southwest monsoon. The fluctuations of intensity of the tropical easterly jet tej and its association with the indian summer monsoon rainfall have been examined using the diagnostics from ncepncar national. The african easterly jet is a region of the lower troposphere over west africa where the seasonal mean wind speed is at a maximum and the wind is easterly. Difference between westerly and easterly jet stream. A study of south asian monsoon convection and tropical. The tropical easterly jet stream tej, whose existence was established by koteswaram 1958, the lowlevel jet stream llj discovered by joseph and raman 1966andfindlater1969,andthetibetananticyclone north of the tej are the important components of the asian summer monsoon system and parts of the mon. Generation of the african easterly jet and its role in. The revised picture of west african monsoon is pointing to a diminished importance of itcz in controlling precipitation while emphasizing the role of african easterly jet aej, tropical easterly jet tej, and low level westerlies as some of the main tropical circulation features in the region 2426.
To understand how jet streams affect indian monsoons, we need to know the basic mechanism of jet stream induced weather conditions. View academics in indian summer monsoon rainfall analysis with tropical easterly jet stream on academia. The disturbances around this zonal circulation pattern, socalled african easterly waves aews, have been identi. The fluctuations of intensity of the tropical easterly jet tej and its association with the indian summer monsoon rainfall have been examined using the diagnostics from ncepncar national centre for environmental predictionnational centre for atmospheric research reanalyses project for the period 1986 to 1994. The tropical easterly jet forms over india through the heating of the eastern flow in high altitude plains. The study of these features is important as they reveal the strength of the monsoon and its yeartoyear variability. Using the national center for environmental prediction and national center for atmospheric research ncepncar reanalysis wind and homogeneous indian summer monsoon ism rainfall data during june, july, august and september jjas for the period of 19532012, a long. The analysis herein using 60 yr 19502009 of data reveals that this. Variations of indian summer monsoon rainfall induce the. Based on observations, reanalysis, and multimodel ensemble mean ensmean simulations of coupled model intercomparison project phase 5 cmip5 models, the responses of wasm rainfall, as well as some relevant. Weakening trend of the tropical easterly jet stream of the boreal. Ppt african monsoon powerpoint presentation free to. Differences from other monsoon systems are probably related to the tropical easterly jet stream.
The arabian sea branch the monsoon winds originating over the arabian. The rain is primarily due to coalescence of droplets, with most. The somali jet the monsoon wind that is deflected to the north as it crosses the equator is further deflected to the east by the mountains of africa. Flohn,investigations on the tropical easterly jet, bonner met. The elements of the monsoon system include pressure of the monsoon trough, pressure of the mascarene high, crossequatorial lowlevel jet, tibetan high, tropical easterly jet, monsoon cloud cover, monsoon rainfall, dry static stability of the lower troposphere, and moist static stability of the lower troposphere. African easterly jet aej, a region of strong zonal winds up to. Characterization of west african jet streams and their. In the case of weak monsoon, over the equatorial indian ocean the anomalies are westerlies, which infer the weakening of easterly jet. The indian summer monsoon ism exists mainly due to landsea heating contrast between indian ocean and asian land. The fluctuations of intensity of the tropical easterly jet tej and its association with the indian summer monsoon rainfall have been examined usin. The easterly winds become very active in the upper troposphere and they are associated with westerly winds in the lower troposphere southwest monsoon winds.
With the development of this jet, the way is cleared for approximately 3,000 metres of powerful, southwest flow of actual monsoon that moves over india and with a more southern flow to china. C10jet streams for upsc iasimpact of jet streams on weather. The progress of the southwest monsoon towards india is greatly aided by the onset of certain jet streams including the crucial somali jet that transits kenya, somalia and sahel and exits the african coast at 9 degrees north at low level and very. Feb 06, 2019 find out the concept given in the jet stream theory and affects of jet stream on the indian monsoon which is very useful for the competitive examinations like upscprelims, ssc, state services. The temperature contrast between the sahara desert and the gulf of guinea causes the jet to form to the north of the monsoon trough. In ealry june, the north eastern indian states receive rainfall due to the effects of the easterly jet stream. Our new crystalgraphics chart and diagram slides for powerpoint is a collection of over impressively designed datadriven chart and editable diagram s guaranteed to impress any audience. Tibetan anticyclone and tropical easterly jet springerlink. An easterly jet emerges over peninsular india with the northward migration of stj.
The foregoing holds on individual days and climatically during the monsoon season as a whole. Easterly anomalies are dominant over the equatorial indian ocean in active monsoon situation. Recent research has reported that the tropical easterly jet stream tej of the boreal summer monsoon season is weakening. The study of these features is important as they reveal the strength of the monsoon and its year. The tropical easterly jet, which is part of the anticyclonic circulation about the asian monsoon high, forms near the tropopause. The indian monsoon is a giant weather system which influences not only the surface winds but also upper winds like jet stream.
On finding these current concepts questionable, this. This jet descends over the indian ocean near madagascar and intensifies its high pressure cell so as to move as southwest monsoon. Permanent jet streams there are two permanent jet streams subtropical jets at lower latitudes and polar front jets at midlatitudes. The west african monsoon wam involves the interaction of multiscale processes ranging from planetary to cumulus scales, which makes it challenging for coarse resolution general circulation models to accurately simulate wam. Interannual fluctuations of the tropical easterly jet and. A later paper will examine more closely the relationship between the wave variability and the west african monsoon, including the rainfall and african easterly jet aej variability. The intensity of tej is found to be well correlated with india summer monsoon. Changing relationship between the tropical easterly jet and.