The Wind-Chill Index

This Lessons from History article about the wind-chill index (WCI) explores historical polar and meteorologic literature relevant to topic presents unpublished work 1939. Geographer Paul Siple (1908–1968) was a 6-time Antarctic explorer scientist who invented named WCI in his doctoral dissertation at Clark University. Charles Passel (1915–2002) performed studies Antarctica 1940 that led publication 1945. paper is often credited as beginning of WCI. Through years critiques revisions by others, these efforts evolved into equivalent temperatures (WCTs) used today. essay history, science, overlooked originality, simplicity, details Siple’s work. The remarkable similarity original chart current shown adapting overlaying 1939 onto WCT with its times-to-frostbite data. writings Siple, Passel, others provide an evocative supporting narrative illustrate some problems living cold environmental conditions. Wind chill phenomenon caused effect wind on heat loss bare human skin, resultant increased rate cooling sensation cold. Wind-chill indices other tools are wilderness nonwilderness weather reporting warn people hazards, particularly frostbite.1US Department Commerce/National Oceanic Atmospheric AdministrationOffice Federal Coordinator Meteorological Services Supporting Research. FCM- R19-2003. Report temperature extreme indices: evaluation improvement projects.http://solberg.snr.missouri.edu/gcc/OFCMWindchillReport.pdfDate accessed: March 12, 2021Google Scholar American geographer It briefly adopted for military purposes referred here because it scale or correlates clinical manifestations parameters temperature. In 1940, another trip Antarctica, effects air humans. Their study published 1945.2Siple P.A. C.F. Measurements dry atmospheric subfreezing temperatures.Proc Am Philos Soc. 1945; 89: 177-199Google one usually cited creation chronicle WCIs related (WCETs simply WCTs). examines comparison charts. terminology can be confusing. interchangeably with, abbreviation for, any several terms. SP 1945 this denote measurements Passel. employed criticized decades until WCTs. may refer individual figure but, depending context, mean whole structure physics, calculations, charted figures. When “the WCT” presented relates grades danger, term (WCTI) correct but not always used. “old refers WCTI based 2001 “new uses updated biophysical models. predicts risk frostbite, so formally WCTI” described official report.1US Despite distinction, terms such WCT,” “2001 “current commonly convective power has long been studied. A compilation 89 early physics-laden references experiments calculations between 1912 1941 included comfort index, power, temperature, scales, effective conditions.3Stone R.G. practical interpretation bioclimatology.Bull Meteorol 1943; 24: 327-339Crossref Google These were realm mathematicians scientists. emerging field studied interaction body environment leaders biophysicist A. Pharo Gagge (1908–1993). 1941, he proposed new units varying specialists could have common system communicating thermal exchanges.4Gagge A.P. Burton A.C. Bazett H.C. description exchange man environment.Science. 1941; 94: 428-430Crossref PubMed Scopus (221) sitting/resting comfortably indoors 21°C (70°F) less than 50% humidity, 1 clo insulation value everyday clothing metabolic task (MET) average-size person rest. Today’s MET ratio which expends energy relative mass while performing specific activity compared sitting/resting. et al. produced brief tables suggesting optimal requirements indoor outdoor conditions.4Gagge forerunners.2Siple definitions restated 1966 engineering changes US Army Research Institute Environmental Medicine (USARIEM), whose mission statement includes enhancement health performance through medical research.5Fiske D.L. CLO. Part 1. Restatement definitions. Technical report 06-21-CM. Advanced projects branch, organic materials division, Natick Laboratories. 1–7. Army, Natick, MA1966Google Similarly, 1966, first institutional standards comfortable airflow Society Heating, Refrigerating Air-Conditioning Engineers, last revised 2020.6ASHRAEThermal Conditions Human Occupancy ANSI/ASHRAE Standard 55-2020. ASHRAE, Peachtree Corners, GA2021: 1-75Google laid groundwork WCI, venue, more memorable term, popularization awaited. scientist. At age 19, Eagle Scout selected national contest accompany Richard E. Byrd, Jr (1888–1957) expedition 1928 1930.7Siple Boy Byrd. GP Putnam’s Sons, New York1931Google Scholar,8Siple 90° South. Story South Pole Conquest. York1959Google recorded day we felt most when down fifty-five degrees [F] below zero [-48°C] there twenty miles hour [32 km·h-1]. One remain out doors only few minutes.”7Siple words inkling future career. On second Byrd (1933–1935), member ice party keenly portrayed conditions real agony comes wind” and, sharply, “like knife drawn across face.”9Murphy C.J.V. lunatic fringe.Byrd RE. Discovery. Second Expedition. York1935Google deemed radically different previous now supply officer group leader, participate biology experiments, head 77-d exploration studying geology, glaciology, biology, findings name.8Siple Scholar,10South-Pole.comByrd Expedition II 1933-35.https://www.south-pole.com/p0000108.htmDate Scholar,11Siple Expedition-Botany. I. Ecology geographical distribution.Ann Missouri Bot Gard. 1938; 25 (Available at:): 467-514https://www.biodiversitylibrary.org/page/16046974#page/477/mode/1upDate 2021Crossref Afterward, earned doctorate geography. naming “wind-chill index” rudimentary formula found 1939.12Siple PA. Adaptation climate Antarctica. Parts 1, 2, 3. pp 1–525. Unpublished dissertation, University Goddard LibraryGoogle occasionally cited, even himself.2Siple multiplying Celsius speed (in m·s-1) correlating product risks travel. results chosen unitless, would never plain again. There had known request time writing, according resource sharing librarian Library (K Stebbins, October, 2020; personal communication). More features provided here. Near conclusion adaptation shows sedimentary paleontologist West Base leader. went south look fossils particular during 87 d exploring dogsled map mountains. His contemporaneous diary An Journal initially limited 200 copies 1995 book Ice.13Ice. F. Lubbock. Texas Tech Univ Press, Texas1995Google autobiographical memoir emphasizing later trips Antarctica.8Siple recalled interview meteorologist Arnold Court occupied collecting radiosonde data, asked help experiment.14Passel C. Goerler R. research center archival program, Feb 13–14, 2000.https://kb.osu.edu/bitstream/handle/1811/6040/passelfinaltranscript.pdf?sequence=1&isAllowed=yDate attributed background interest subject.”13Ice. Scholar,14Passel Returning home own material master’s degree geology served Marine Corps. Passel’s made correlations “between rates states comfort.”2Siple Final their landmark much delayed events December 1941. During World War II, Captain evaluated cold-weather joined Office Development civilian scientist.8Siple Scholar,15Siple General principles governing selection climates. In: Reports scientific United States Service Expedition, 1939–1941.Proc 200-234Google devoted 26 pages era extensive winter gear supplementary paper.12Siple Modern solved older clothing. began 1956 Amundsen-Scott Station inaugural science leader International Geophysical Year (IGY) 1957–1958. history WCTs continues forward 1940s return after that. Leading up 1940/1945 study, aware thermogenesis, values subcutaneous tissues, vasoconstriction, variability, more, career added disclaimer physiology textbooks should consulted. He recognized qualitative represented “a factor climatic sensible certain extent, although indicate exact proportion effect. To calculate measure true entail cumbersome process probably give better picture wind-chill.”12Siple prove substantial understatement. wrote needed limit complicating factors humidity solar gain. conveniently avoided dark dead winter. noted insensible losses addressed corrections.2Siple With knowledge chamber John B. Pierce Hygiene Laboratories proceeded quantitatively perform carefully “measurement temperatures."2Siple They opine that, library methodology biased all studies.2Siple set aside elementary part did actually loss.2Siple Instead, constructed “relative thermometer” 10-m pole, stating “I experiment try took small cylinder water freeze. Charlie helped me accurately length remained freezing point letting crystallization under nearly 100 combinations velocity temperature.”8Siple anemometer speed. Rather thermometer, thermohm measured electrical resistance platinum wire cylinder. separate naked ambient From observational “runs” speeds absence insolation (solar radiation) ignoring evaporation factors, data recorded.2Siple cylinder, attention 0°C giving fusion. By knowing property, time, water, surface area, they calculated kcal·m-2·h-1.2Siple typically 3- 4-digit neither nor resemble like relationship use. inanimate test no feelings, physics-based correlated sensations parties various combinations. For example, paper’s Table 5 times elapsed sudden pain blanching cheek, frostnip.16McIntosh S.E. Freer L. Grissom Auerbach P. Rodway G. Cochran al.Wilderness Medical practice guidelines prevention treatment frostbite: 2019 update.Wilderness Environ Med. 2019; 30: S19-S32Abstract Full Text PDF (18) 7 column numbers indexed descriptors column. titled “stages cooling.”2Siple range 0 (“nude sun-bathing possible”) 2600, including 2300 where “exposed areas face will freeze within 1/2 minute.”2Siple reading 3290 IGY 1957 indicates “little chance lengthy survival.”8Siple Another example 2000, signifying “travel temporary shelter becomes dangerous.”2Siple That closely echoes 1939, 500 “conditions dangerous travel shelter.” As 1945, 2 indices. uncomplicated still popular services.2Siple WCI.2Siple preliminary table way polar, military, climatology usage publications.14Passel Scholar,17Court chill.Bull 1948; 29: 487-493Crossref final form decades. Pragmatic rules thumb also commonplace. personnel Alaska 1964 taught “rule 30s.” -30°F (-34°C) 30 mph (13 m·s-1), frostbite s former Specialist 4 (I. Coddington, December, 1948, aforementioned focused chill, “no precise explanation critical discussion method computation heretofore appeared.”17Court working mention graphs tables. work, disagreed units, rightly consider complex ways exchanged surroundings. compliment low temperatures.17Court section accompanying 1951 35 workers’ subjective outdoors Saskatchewan, audaciously declared objective numerical indicator someday make subjectivity unnecessary.18Currie B.W. Sensations isopleths wind-temperature diagram Canadian prairies.Bull 1951; 32: 371-374Crossref 1960, displeasure continued, recommended “just numbers,” perhaps harkening back what plainly did.19Siple windchill - conference discussion. Molnar G.in: Horvath S.M. Cold injury. Transactions Sixth Conference. Josiah Macy Jr. Foundation, York1960: 216-218Google Scholar,20Osczevski basis chill.Arctic. 1995; 48: 372-382Crossref continued defensively: “looking back, rather too naive approach, assumptions little careless. standpoint, I think schema use.”19Siple useful, modifications come. portrayal eventually changed type intuitively understood regular users “feels like” Equivalent express conditions, context here, mathematically computed colder temperature-like figures exposed same if present.1US Scholar,21Kessler errors.Bull 1993; 74: 1743-1744Crossref Defense interested developing operational indices.1US 1961, Armored Laboratory (AMRL) Fort Knox, Kentucky, consolidated laboratories USARIEM Massachusetts. AMRL’s 1961 despite unrealistically awkward design, AMRL 1963 textbook.22Meteorological measurements.in: Consolazio Johnson R.E. Pecora L.J. Physiological Metabolic Functions Man. McGraw-Hill, York1963: 413Google 1967, site Air Force Arctic Aeromedical Ladd AFB, Alaska, became Lab, subsidiary USARIEM, Garrison Wainwright. 1965 Eagan identified chart.23Eagan Effect movement power.in: Kolb Holstrom Review regions. documentary No. AAL-TDR-64-28. Garrison, Wainwright: Aerospace, Division, Systems Command Test Center, Evaluation Command. Materiel Command, 1964: 147-156Google chart, warmer version. easier use being WCTI. source Eagan’s stated. printed charts pocket cards.23Eagan natural convection around produces “wind” 0.9 m·s-1 (2 mi·h-1) do stand move themselves limbs 1.8 (4 mi·h-1). Baseline necessitated correction earlier WCTs.23Eagan Scholar,24Bluestein M. factor: development applicability.J Biomech Engin. 1998; 120: 255-258Crossref (27) definition walking decreased 1.3 (3 revision.1US 1970s, supplant WCI.1US t