In summer the subtropical easterly jet blows over peninsular india approximately at 14 o n and bring some rain and storm. African easterly waves aews are an important part of the west african and tropical atlantic climate. Jetstreams polar, subtropical, tropical easterly, somali. There are different jet streams and in respect of the climate and monsoons of india it is the subtropical jet stream stj and. Sahel rainfalltropical easterly jet relationship on synoptic. Climatologywind wikibooks, open books for an open world. In ealry june, the north eastern indian states receive rainfall due to the effects of the easterly jet stream. Subtropical westerly jet streams n sub tropical easterly jet. Jetstreams polar, subtropical, tropical easterly, somali jetstreams. Abstract 1 using highvertical resolution indian mesospherestratospheretroposphere mst radar and gps sonde observations from gadanki. During summer, there is a presence of easterly jet streams. Antonyms for tropical easterly jet stream include jet stream, air stream, geostrophic wind, gradient wind, highaltitude wind, highspeed wind stream, prevailing wind and upperatmosphere wind. Despite their importance, very little is known about the.
The subtropical jet stream plays a significant role in both hindering the monsoon winds as well as in quick onset of indian monsoons. Climate of india notes exam preparation exams daily. Related to easterly n westerly trade winds respectivelyanonymous. The african easterly jet aej is one of the most complex and intriguing dynamical features in tropical meteorology. So one needs to look at seasonal scales to explain the formation of the so called tropical easterly jet stream. The strongest development of the jet is at about 15 km above the earths. These jets, like the polarfront jets, are best developed in winter and early spring. Jet stream is a upper atmospheric circulation created by the thermal variation between surface and upper atmosphere and equator and poles. African easterly wave variability and its relationship to. Both the northern and southern hemispheres have jet streams, although the jet streams in the north are more forceful due greater temperature gradients. The modernera retrospective analysis for research and applications.
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. The african easterly jet south aejs is an important feature of the central african mid tropospheric circulation and has been identified as a key contributor to convection over the region. Stratiform precipitation production over subsaharan. Limate i national council of educational research and. Tropical easterly jet stream meteorology britannica. While the polar and subtropical jet streams are the best known and most studied, other jet streams can form when wind speeds are above 94 kph in the upper atmosphere at about 9 14. Jan 21, 2016 indian monsoons role of tropical easterly jet tej, indian monsoons role of tibet, indian monsoons role of somali jet and indian monsoons role of indian ocean dipole. This paper, however, assesses the role of an upper troposphere synoptic feature of importance in modulating surface rainfall over sudan in the eastern sahel. 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. Indian monsoons role of tropical easterly jet tej african easterly jet, indian monsoons role of tibet, indian monsoons role of somali jet and indian monsoons role of indian ocean dipole. The burst of monsoons depends upon the upper air circulation which is dominated by sub tropical jet streams stj.
The sub tropical jet stream plays a significant role in both hindering the monsoon winds as well as in quick onset of indian monsoons. Above the lowlevel westerlies, and distinct from the harmattan easterlies and the tropical easterly jet, is the african. Towards the end of may, a narrow stream of air, which moves from the west to the east over northern india, suddenly weakens and moves to a new location far to the north of the himalayas. It is then replaced by the tropical easterly jet stream. The westerly sub tropical jet stj is found in the north of this high and tropical easterly jet tej in the south of it fig4. The south west monsoon coming in india is related to tropical easterly stream. The wind near the aej moves faster than the surrounding air, causing eddies small whirlwinds to develop. Mean position of tibetan high at 200hpa tropical easterly jet tej south of the sub tropical ridge over asia, the easterly flow concentrates into. Subtropical westerly jet streams n sub tropical easterly jet streams blow in winter n summer respectively these win ds r cool, arid, contain moisture, dry or hot social science. Subtropical jet stream article about subtropical jet. Longterm trends and their features during active and break monsoon phases, j. Coriolis force an apparent force that as a result of the earths rotation, deflects moving objects like air currents to the right in the northern hemisphere and to the left in the southern hemisphere. Characterization of west african jet streams and their.
This study investigates the structure of the african easterly jet focusing on instability processes on a seasonal and sub seasonal scale, with the goal of identifying features that could provide increased predictability of atlantic tropical cyclogenesis. They are known both to modulate the daily rainfall over west africa e. Western cyclonic disturbances the western cyclonic disturbances are weather. Climate class 9 notes geography chapter 4 learn cbse. These jet streams are located 5060 northsouth of the equator and at 35,000 feet about 6. During summer, in the northern hemisphere, the subtropical jet weakens considerably, and it is only identifiable in sporadic velocity s. Subtropical westerly jetstream the monsoons all over the world are experienced in the tropical area only, roughly between 20 n and 20 s. Jet streams significantly influence the south west monsoons swms in the indian subcontinent. As explained by maam,its path is from somalia to tibetian plateau. Differences from other monsoon systems are probably related to the tropical easterly jet stream.
The southwest monsoon dominates the weather, and clouds and rain abound. Mar 15, 2017 an easterly jet stream, called subtropical easterly jet stream, blows over peninsular india approximately over 14 n during the summer months. Moreover, the tej over west africa is significantly correlated with summer sahel rainfall on interannual and decadal time scales. The main jet streams are in middle and subtropical latitudes. 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.
Difference between westerly and easterly jet stream. An easterly jet stream, called the sub tropical easterly jet stream blows over peninsular india, approximately over 14n during the summer months. Tropical equatorial easterly jet stream tejs 14n this jet is a prominent feature of the upper air circulation during the indian summer monsoon season june september. Unlike the polar front jet stream, it travels in lower latitudes and at slightly higher elevations, owing to the increase in height of the tropopause at lower latitudes. The change from a westerly direction in winter to an easterly one in summer influences the surface wind 3 changes that mark the summer monsoon 4. The rain is primarily due to coalescence of droplets, with most of the clouds located below 3,500 metres 11,500 feet. As the winter season progresses into the spring and summer, temperature in south asia rises and the southern branch of the westerly polar jet stream changes abruptly to the north of the himalayas.
The southwest monsoon season jun sep part 2 civilsdaily. Tibetan anticyclone and tropical easterly jet springerlink. It raises a number of questions, ranging from its formation mechanism to its maintenance, and from the causes of its intensity fluctuations to its role. Results demonstrate that aejs is dominated by rotational. This jet implies a deep layer of warm air to the north of the jet and colder air to the south over the indian ocean. Subtropical westerly and tropical jet streams certain interesting changes take place in the upper atmosphere with the advent of the summer monsoon. Limate i national council of educational research and training. It is the main causative factor for determining the vigour of the summer monsoon in india. 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. Jul 21, 2019 many tropical waves are generated by the african easterly jet aej, an easttowest oriented wind much like the jet stream that flows across africa into the tropical atlantic ocean. What is the opposite of tropical easterly jet stream. In summer, the subtropical westerly jet stream moves north of the himalayas with the apparent movement of the sun.
Mar 10, 2018 jetstreams polar, subtropical, tropical easterly, somali jetstreams. Sub tropical westerly and tropical jet streams certain interesting changes take place in the upper atmosphere with the advent of the summer monsoon. Subtropical jet stream, a belt of strong upperlevel winds lying above regions of subtropical high pressure. 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. 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.
To investigate the subdaily variation in tropical easterly jet tej, a few special experiments have been conducted with mesospherestratospheretroposphere mst radar located at gadanki. This study uses 21year 19832003 reanalysis data sets of erainterim, ncep2 and merra2 to establish mechanisms related to aejs dynamics. The sub tropical easterly jet stream blowing over peninsular india is responsible for the tropical cyclones that affect the eastern coastal regions of india during the monsoon as well as during the october to november period. Indian monsoons role of tropical easterly jet tej, indian monsoons role of tibet, indian monsoons role of somali jet and indian monsoons role of indian ocean dipole. Subtropical easterly jetstream jet streams important for northeast monsoon. It intensifies the formation of jet streams, its extension as well as its velocity. Prabhakara rao 2009, characteristics of the tropical easterly jet. Generation of the african easterly jet and its role in. Jun 04, 2017 jet stream is a upper atmospheric circulation created by the thermal variation between surface and upper atmosphere and equator and poles. The lowlevel easterly african jet stream is considered to play a crucial role in the southwest monsoon of africa, and helps form the tropical waves which move across the tropical atlantic and eastern pacific oceans during the warm season. The tropical easterly jet tej is a characteristic upperlevel feature of the west african monsoon wam circulation.
Tropical easterly jet stream it occurs near the tropopause over southeast asia, india, and africa during summer. Permanent jet streams there are two permanent jet streams subtropical jets at lower latitudes and polar front jets at midlatitudes. An easterly jet stream, called the subtropical easterly jet stream blows over peninsular india, approximately over 14n during the summer months. Subdaily variations observed in tropical easterly jet tej. The westerly subtropical jet stj is found in the north of this high and tropical easterly jet tej in the south of it fig4. The subtropical easterly jet stream blowing over peninsular india is responsible for the tropical cyclones that affect the eastern coastal regions of india during the monsoon as well as during the october to november period. Indian monsoon mechanism and the role of sub tropical jet streams. Many tropical waves are generated by the african easterly jet aej, an easttowest oriented wind much like the jet stream that flows across africa into the tropical atlantic ocean. This study investigates the structure of the african easterly jet focusing on instability processes on a seasonal and subseasonal scale, with the goal of identifying features that could provide increased predictability of atlantic tropical cyclogenesis. Jan 02, 2016 both the northern and southern hemispheres have jet streams, although the jet streams in the north are more forceful due greater temperature gradients.
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. Subtropical jet stream stj the subtropical jet stream is produced by the earths rotation coriolis. From these two pioneering papers koteswaram tej and raghavan k tej 1973 available behind a paywall, reproduced here origin of tropical easterly jet, there exists at the upper levels an anticyclone over the indian subcontinent. Find out information about sub tropical jet stream. It basically flows at a height of 7 to 10kms from the surface of earth from west to east in a meander path.
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