Editing Gilbert Walker (physicist) (section)

==Career==
[[Henry Francis Blanford]], the founding director of the [[Indian Meteorological Department]], had noticed the pattern that the summer monsoon in India and Burma was correlated with the spring snow cover in the Himalayas and it became routine to use this to make predictions of the Indian monsoons.  By 1892 however, these predictions began to fail and the second director [[John Eliot (meteorologist)|John Eliot]] began to use several other correlations including strength of the trade winds, anticyclones, Nile floods and data from Australia and Africa. Eliot's forecasts from 1899 to 1901 failed so badly, with a drought and famine when he predicted higher than normal rains, that he was criticized severely by the newspapers leading to forecasts being made confidential from 1902 to 1905. A growing interest in the work of [[Brückner-Egeson-Lockyer cycle|Lockyer on cycles]] led him to choose a mathematically inclined successor who would be Walker, despite his lack of experience in meteorology. Eliot himself was an able mathematician, a [[Wrangler (University of Cambridge)|Second Wrangler]] at Cambridge, while Walker had been a [[Senior Wrangler (University of Cambridge)|Senior Wrangler]]. Walker was an established applied mathematician at the [[University of Cambridge]] and gave up a Fellowship at Trinity to take up a position as assistant to the meteorological reporter in 1903.<ref>{{Cite journal|last=Normand|first=Charles|date=1953|title=Monsoon seasonal forecasting|journal=Quarterly Journal of the Royal Meteorological Society|language=en|volume=79|issue=342|pages=463–473|doi=10.1002/qj.49707934202|bibcode=1953QJRMS..79..463N}}</ref> He was elevated to the position of director general of observatories in India in 1904.<ref name="IndianBio">{{cite IBD1915|wstitle= Walker, Gilbert Thomas |volume= 24.1 |page= 456 |year=1915|short=}}</ref><ref>{{cite journal|title=On the Connexion of the Himalaya Snowfall with Dry Winds and Seasons of Drought in India |author=Blanford, H.F.|year=1884| pages=3–22| journal=Proceedings of the Royal Society of London|volume=37|issue=232–234| doi=10.1098/rspl.1884.0003|bibcode=1884RSPS...37....3B|s2cid=140682519|url=https://zenodo.org/record/1432075}}</ref> Walker developed Blanford's idea with quantitative rigour and came up with correlation measures (with a lag) and regression equations (in time-series terminology, [[Autoregressive model|autoregression]]). He set up a group of Indian clerks to calculate correlations between weather parameters.<ref>{{cite journal| author=Walker, G.T.|year=1923| title= Correlation in seasonal variability of weather, VIII. A preliminary study of world weather.| journal=Memoirs of the India Meteorological Department| volume=24| pages=75–131}}</ref> The methods he introduced for time-series regression are now partly named after him (the other contributor was [[Udny Yule]] who studied sun-spot cycles) as the Yule-Walker equations.<ref name=katz>{{cite journal| journal=Statistical Science| year=2002| volume=17| issue=1| pages=97–112| title= Sir Gilbert Walker and a Connection between El Niño and Statistics| author=Katz, Richard W.| url=http://projecteuclid.org/download/pdf_1/euclid.ss/1023799000| doi=10.1214/ss/1023799000| citeseerx=10.1.1.506.8097}}</ref> Analyzing vast amounts of weather data from India and lands beyond, over the next fifteen years he published the first descriptions of the great seesaw oscillation of [[Earth's atmosphere|atmospheric]] [[pressure]] between the Indian and [[Pacific Ocean]], and its correlation to [[temperature]] and [[rain]]fall patterns across much of the Earth's tropical regions, including India. This is now called the [[El Niño Southern Oscillation]].<ref>{{cite journal|author=Khandekar, M.L.| year=1991| title= Eurasian snow cover, Indian monsoon and El Niño/Southern Oscillation – a synthesis| journal= Atmosphere-Ocean| volume= 29| issue=4| pages= 636–647| doi=10.1080/07055900.1991.9649422| bibcode=1991AtO....29..636K}}</ref><ref>{{cite journal| journal=Quarterly Journal of the Royal Meteorological Society| title=World Weather| author=Walker, Gilbert| volume=54| issue=226| year=1928|pages=79–87| doi=10.1002/qj.49705422601| bibcode=1928QJRMS..54...79W}}</ref><ref>{{Cite journal|last1=Shukla|first1=J.|last2=Paolino|first2=Daniel A.|date=1983|title=The Southern Oscillation and Long-Range Forecasting of the Summer Monsoon Rainfall over India|journal=Monthly Weather Review|language=en|volume=111|issue=9|pages=1830–1837|doi=10.1175/1520-0493(1983)111<1830:tsoalr>2.0.co;2|bibcode=1983MWRv..111.1830S|issn=0027-0644|doi-access=free}}</ref><ref>{{Cite journal|last=Walker|first=Gilbert T.|date=1933|title=Seasonal Weather and its Prediction*|journal=Nature|language=en|volume=132|issue=3343|pages=805–808|doi=10.1038/132805a0|bibcode=1933Natur.132..805W|issn=0028-0836|doi-access=free}}</ref><ref>{{cite journal|author=Pisharoty, P. R.|year=1990|title=Sir Gilbert Walker—pioneer meteorologist and versatile scientist|url=https://www.currentscience.ac.in/Downloads/article_id_059_02_0121_0122_0.pdf|journal=Current Science|volume=59|issue=2|pages=121–122|access-date=6 July 2019|archive-date=1 August 2020|archive-url=https://web.archive.org/web/20200801011831/https://www.currentscience.ac.in/Downloads/article_id_059_02_0121_0122_0.pdf|url-status=dead}}</ref> He was made a Companion of the [[Order of the Star of India]] in 1911.<ref name="IndianBio" />

Walker took an interest in several other fields. He made mathematical studies on bird flight and boomerangs. An interest in boomerangs as an undergraduate had earned him the nickname of "Boomerang Walker". In [[Shimla]], he used to throw a boomerang on the grounds of Annandale attracting the attention even of the Viceroy of India.<ref>{{cite journal|author=Walker, G.|year=1897| title=On boomerangs.| journal=Phil. Trans. R. Soc. A | volume=190|pages=23–42|jstor=90722|doi=10.1098/rsta.1897.0013|bibcode=1897RSPTA.190...23W|doi-access=free}}</ref> He found faults in the ideas on bird flight by [[Ernest Hanbury Hankin]], fellow Cambridge scientist at Simla, and pointed out that ascending thermals had enough energy to support the soaring of birds and also pointed out the role of turbulent eddies in providing lift.<ref>{{cite journal
| last1=Walker | first1=G.
| date=1923
| title=Meteorology and the non-flapping flight of tropical birds
| journal=[[Mathematical Proceedings of the Cambridge Philosophical Society]]
| volume=21
| pages=363–375
| url= https://archive.org/stream/proceedingscambr21camb#page/362/mode/2up}}</ref><ref name=pen>{{cite journal| author=Walker, J.M.|year=1997| title= Pen portraits of presidents—Sir Gilbert Walker, CSI, ScD, MA, FRS.| journal=Weather| volume=52|issue=7| pages=217–220 |doi=10.1002/j.1477-8696.1997.tb06313.x|bibcode=1997Wthr...52..217W| doi-access=free}}{{open access}}</ref><ref>{{cite journal|author=Walker, G.|year= 1925| title=On the wings of gliding birds. | journal=J. Proc. Asiat. Soc. Bengal| volume=20|pages=243–6}}</ref> He published a summary of his ten years of research in ''Nature'' in 1901.<ref>{{cite journal|title=Boomerangs|author=Walker, G.T.| journal=Nature| volume=64|issue=1657|pages=338–340 |year=1901|doi=10.1038/064338a0|url=https://zenodo.org/record/1429406}}</ref> He was an accomplished flute player and took an interest in the physics of the flute. He was also an expert on the history and evolution of the flute. He made some design changes to flutes and these went into manufacture.<ref>{{cite journal| author=Sheppard, P.A. |year= 1959| title= Obituary of Sir Gilbert Walker, CSI, FRS. | journal= Quarterly Journal of the Royal Meteorological Society| volume=85| issue=364| page=186 | doi = 10.1002/qj.49708536423 }}</ref> He was also a watercolour artist and while at Shimla, held an exhibition of his works.<ref name=pen />