1. Prof. P. KOTESWARAM AND 50 YEARS OF TROPICAL EASTERLY JETSTREAM
Dr. P.V.Joseph
Professor Emeritus, Department of Atmospheric Sciences, Cochin University of Science and Technology

2. Prof Pancheti Koteswaram was born on 25 March 1915
He obtained D.Sc degree in Physics of the University of Madras in 1939
In 1940 he joined the India Meteorological Department (IMD) as Asst. Meteorologist at Calcutta (now Kolkata)
In 1969 he became Director General of Meteorology of IMD and continued in the post till During this period as permanent representative of India, he was elected vice- president of WMO in 1971

3. High lights of Prof. Koteswaram’s Work in IMD (1940-1975)
Prof. Koteswaram learned Meteorology while working in the operational offices of IMD as at that time there was no formal met. training school in India
During his 35 years in IMD he worked hard to improve IMD and make it a world class institution in weather forecasting and warning services, in meteorological research and in international co-operation
Persons like me who were associated with him for many years knew him as a good operational meteorologist (forecaster), a good research worker, a good administrator cum manager and above all a person deeply interested in the welfare of the officers and staff working with him

4. High lights of Prof. Koteswaram’s Work in IMD (Contd.)
As Director of aviation services in IMD Prof. Koteswaram set up extended analysis and prognosis centers at Bombay, Calcutta, Madras and New Delhi
As Deputy DGM at Pune he developed a computerized Climatological data center at that office
He persuaded the Global Atmosphere Research Programme (GARP) to take up research on Asian summer monsoon. His voice was heard and an agreement was reached that MONEX (Monsoon Experiment) would be a part of the First GARP Global Experiment (FGGE) to be conducted late in 1970 s

5. High lights of Prof. Koteswaram’s Work in IMD (Contd.)
The most important work of Prof. Koteswaram as DGM of IMD was to organize cyclone detection, tracking and warning as an efficient operational system
He set up 10 Cyclone Detection Radars (S-band), 4 along the west coast and 6 along the east coast of India (IMD is now converting them to Doppler radars)
He also worked very hard and set up Cyclone Distress Mitigation committees in all the coastal states of India comprising of administrators (Government), engineers and meteorologists with the task of drawing up contingency plans, educating the public, prompt evacuation of costal population from cyclone risk areas, construction of cyclone shelters and arranging for fast and reliable communication of cyclone warnings

7. Prof. Koteswaram In the International Arena
He was Visiting Professor at the University of Miami in 1965, and worked at the National Hurricane Research Laboratory and the National Centre for Atmospheric Research at Boulder in USA.
During the Sixth World Meteorological Congress in 1971, as a follow-up to the UN Resolution on Tropical Cyclones which followed the unprecedented loss of life in Bangladesh, he was designated as chairman of a WMO committee of experts to develop a plan that launched the WMO Tropical Cyclone Project.
As a member of the WMO Commission for Aeronautical Meteorology he contributed actively to the preparation of Procedures for Air Navigation Services: Meteorology (PANSMET).

8. Research contributions of Prof. Koteswaram
Dr Koteswaram has made significant contributions not only to Indian meteorology and economic development but also to international meteorology.
During 1955–1956, he discovered the existence of the Tropical Easterly Jetstream (Tellus 1958) and found that it was a constant feature between the East China Sea and the Atlantic ocean during the Asian summer monsoon, being strongest over the Indian subcontinent. This discovery won him international recognition and acclaim. We will see more about this feature soon

9. Prof Koteswaram receives Padma Bhushan
It was a proud moment for Prof Koteswaram, for his family and friends in the meteorological and hydrological communities when the President of India conferred on him the prestigious title of Padma Bhushan in January 1975, in recognition of his outstanding services in the field of atmospheric sciences.
The commitment, determination and foresight of Prof Koteswaram as well as his affable personality should be a source of inspiration to meteorologists, hydrologists and indeed the whole scientific community.

10. Tropical Easterly jet Stream at 200 hPa on 25 July 1955 Jet axes marked by heavy broken lines. The subtropical Westerly Jetstream is seen at top left. –from Koteswaram (1958), TELLUS

11. RS/RW stations whose data were used for the study

12. Schematic model of the vertical circulation in the Asian summer monsoon - Koteswaram (1958), Symposium, Monsoons of the World

13. Importance of the discovery of TEJ
Research on monsoon in India till the 1950s was restricted to the Indian subcontinent. Researchers studied features of the Indian monsoon like Monsoon Depressions, Monsoon Trough and its north south oscillations, Active and Break monsoons, influence of orography on rainfall, off-shore troughs and vortices and droughts and floods in the monsoon.
Discovery of the TEJ showed for the first time that a feature connected with the monsoon (TEJ) extended from the south China sea to west Africa
In the 1960 s and later several discoveries came making Indian monsoon a global feature

14. In his paper presented at the Symposium of Monsoons of the World where Prof. Koteswaram gave a schematic model of the vertical circulation of the monsoon, he had suggested two ideas
1) “Tropical cyclones are conspicuous by their absence over the areas overlaid by the Easterly Jetstream (Arabian sea and Bay of Bengal). Such storms generally occur in these two sea areas either before the setting of the Easterly Jet (pre-monsoon season) or after its withdrawal (post-monsoon season) ”. We now know that it is so because of the high vertical wind shear under the TEJ during monsoon.

15. 2) “The location of the Easterly Jetstream seems to influence the pattern of monsoon rainfall. Climatological distribution of rain over south Asia indicates its occurrence down stream from the region of highest winds to the left of the jet stream and upstream to the right. This is found to be true even on individual occasions”. The concept of a high speed center in TEJ and the convergences and divergences in its four sectors (Jet entrance and Jet exit both left and right) have been illustrated in a recent article by Webster and Fussulo (2003) in a six volume encyclopedia of Atmospheric Sciences edited by JR Holten, JA Curry and JA Pyle .

17. The Globalisation of Indian Monsoon continued during the 1960 s.
Ramaswamy (Tellus 1962) showed that breaks in the Indian summer monsoon as a phenomenon of interaction between the Easterly and the Subtropical Westerly Jetstreams
Research by Bunker (1965), Joseph and Raman (1966), and Findlater (1969) showed that lower tropospheric monsoon circulation is dominated by a cross equatorial Low Level Jetstream

18. Deep troughs in Westerlies intrude into India during Break Monsson in the middle and upper troposphere (Ramaswamy 1962, Tellus)

19. Cross-equatorial Low Level Jetsream wind (Findlater 1969)

20. Horizontal and vertical wind shears in Low Level Jetstream over India in July- Joseph and Raman 1966

21. Work in late 1960s by Koteswaram showed that the meridional wind in the TEJ has maximum strength over the equator. If he knew this in 1958 and if he knew about the cross equatorial Low Level Jetstream he would not have put the downward limb of the Reverse (Monsoon) Hadley Cell at the equator.

22. Zonal winds in mean TEJ at 150 hPa
Zonal winds in mean TEJ at 150 hPa. Isotachs at 2m/s intervals- from Koteswaram (1969). (Easterlies by dotted lines)

23. Meridional winds in mean TEJ at 150 hPa
Meridional winds in mean TEJ at 150 hPa. Isotachs at 2m/s intervals- from Koteswaram (1969) (Northerlies by dotted lines)

24. Weakening of Monsoon Wind Flow through Peninsular India
1950 to 2003 at 850hPa (1.5 Km ASL)
Joseph and Anu Simon, (2005) Current Science & Clivar Exchanges

25. Active Break cycle of Monsoon
Joseph and Sijikumar (2004) J.Climate

26. Number of Break Monsoon Days in a Monsoon Season
(wind through India less than 9m/s) during 1950 to 2003
Joseph and Anu Simon, (2005) Current Science & Clivar Exchanges

27. Mean 100 hPa Zonal Wind (Top) and (Bottom) using NCEP data (after Sathiyamoorthy 2005)
m/s

28. Mean 100 hPa Zonal Wind ( ) minus mean of ( ) using NCEP data (after Sathiyamoorthy 2005)
m/s

29. THANK YOU