En­gi­neer re­fined for­mula to cal­cu­late wind chill

Honolulu Star-Advertiser - - IN MEMORY - By Amisha Pad­nani

On frigid win­ter morn­ings, when weather fore­cast­ers are try­ing to de­scribe whether it’s a hat-scarf-gloves day or if just a warm coat will do, they will take the tem­per­a­ture (T) and wind speed (V) and plug the numbers into a handy equa­tion: WCT = 35.74 + 0.6215T - 35.75(V0.16) + 0.4275T(V0.16).

The re­sult is the wind chill in­dex, a num­ber that at­tempts to tell us how cold it might feel rather than sim­ply how cold it is. It con­sid­ers wind, in ad­di­tion to tem­per­a­ture, to cal­cu­late the loss of heat from the body.

The Na­tional Weather Service had been cal­cu­lat­ing the wind chill since the 1970s, but not very ac­cu­rately, un­til two sci­en­tists set out in 2001 to per­fect the mea­sure and make it more re­li­able. One of the two was Mau­rice Bluestein, who died at 76 on Aug. 28 in Pom­pano Beach, Fla., where he lived. His daugh­ter Karen Bluestein said the cause was esophageal cancer. Mau­rice Bluestein, who was trained as a me­chan­i­cal en­gi­neer, had not given much thought to the sci­ence be­hind the weather un­til he was shov­el­ing out his daugh­ter’s car from un­der a snow­drift one evening in Jan­uary 1994 in Indianapolis.

It was the cold­est day on record in In­di­ana, with tem­per­a­tures reach­ing 25 de­grees be­low zero Fahren­heit. The Weather Service, us­ing the ex­ist­ing wind-chill for­mula, de­ter­mined that with winds of about 15 mph, the air tem­per­a­ture could feel as if it were 65 de­grees be­low zero — ca­pa­ble of caus­ing frost­bite within 15 sec­onds. Stay in­doors, the service ad­vised.

But as he shov­eled away, Bluestein found that it re­ally did not feel all that cold. “He kept tak­ing off lay­ers of cloth­ing,” Karen Bluestein said in a tele­phone in­ter­view. “He was sweat­ing, think­ing: ‘This makes no sense. I won­der who came up with this.’” He set out to im­prove what he deemed an in­ac­cu­rate, and alarmist, mea­sure­ment for wind chill. “The old sys­tem scared peo­ple into tak­ing un­nec­es­sary ac­tions,” Bluestein told The Wausau Daily Her­ald in Wis­con­sin 2001. “There are schools, for in­stance, that close at cer­tain wind-chill tem­per­a­tures when per­haps they shouldn’t be closed.” The two sci­en­tists who de­vel­oped the orig­i­nal sys­tem, Paul Si­ple and Charles Pas­sel, based their re­search in the 1940s on a sim­ple ex­per­i­ment: They hung wa­ter bot­tles from a pole on the roof of their re­search build­ing and mea­sured how quickly the wa­ter lost heat (or how quickly the wa­ter turned to ice). At the same time, they mea­sured the sur­round­ing air tem­per­a­ture and wind speed.

They found that the higher the wind speed, the faster the wa­ter froze. For peo­ple, that meant the windier it was, the faster they lost heat and the colder they felt.

Bluestein found nu­mer­ous flaws with the ex­per­i­ment. The re­searchers had as­sumed that the tem­per­a­ture of hu­man skin was 90 de­grees Fahren­heit (it was closer to 50 de­grees on a re­ally cold day); they had placed the con­tain­ers 33 feet above the ground, where wind speeds are higher (rather than the height of a per­son); and they took their mea­sure­ments where it is far colder than where most peo­ple live. Bluestein ru­mi­nated over the prob­lem for sev­eral years, un­til he went to a con­fer­ence and met Ran­dall Osczevski, a Cana­dian sci­en­tist, who had also been ques­tion­ing the wind-chill for­mula.

The two be­gan study­ing wind chill and wrote pa­pers about their find­ings, draw­ing the at­ten­tion of both the U.S. and Cana­dian gov­ern­ments in 2001. Soon they were en­listed by both coun­tries to de­velop a new for­mula.

As part of the project they con­ducted a se­ries of ex­per­i­ments with 12 peo­ple, male and fe­male, mea­sur­ing heat loss from the face in cold and wind as they walked on tread­mills in a wind tun­nel at dif­fer­ent tem­per­a­tures. A “wet trial” sprayed par­tic­i­pants’ faces with a splash of wa­ter every 15 sec­onds to mea­sure whether the pres­ence of pre­cip­i­ta­tion would make peo­ple feel colder. Af­ter plot­ting the data, they found that in some cases the orig­i­nal wind chill in­dex was off by just a few de­grees, but that the dis­crep­ancy grew at higher wind speeds. It con­firmed what many me­te­o­rol­o­gists had al­ready sus­pected: The old cal­cu­la­tion had ex­ag­ger­ated.

Mau­rice Bluestein was born on Jan. 1, 1941, in the Bronx to im­mi­grants from Poland.

He was ac­cepted for ad­mis­sion by the City Col­lege of New York at 16 and earned his en­gi­neer­ing de­gree in 1962. He re­ceived a mas­ter’s in me­chan­i­cal en­gi­neer­ing from New York Univer­sity in 1964 and a Ph.D. in biome­chan­i­cal en­gi­neer­ing from North­west­ern Univer­sity in 1967.

He taught me­chan­i­cal en­gi­neer­ing at In­di­ana Univer­sity-Pur­due Univer­sity Indianapolis for about 19 years.


Mau­rice Bluestein, shown at his desk in the 1960s, was a me­chan­i­cal en­gi­neer whose work helped the Weather Service to gauge wind chill more ac­cu­rately. Bluestein died on Aug. 28 at age 76.

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