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Technical Note: Trees and Wind: Wind Scales and Speeds

Scott Cullen
Arboriculture & Urban Forestry (AUF) September 2002, 28 (5) 237-242; DOI: https://doi.org/10.48044/jauf.2002.036
Key Words

NEED AND PURPOSE

Arborists and urban foresters frequently refer to “wind loads,” “sail areas,” and so forth when discussing the risk of tree failure. Whether the discussion is generally descriptive or specifically quantitative, wind speed is an essential consideration. Wind load is a function of wind speed. Acceptable levels of risk must be associated with wind speeds and their probability of recurrence (Cullen 2002a).

It is conventional in scholarly literature to cite wind speed in SI (Systeme International) units of m/s (NIST, no date). It is customary, however, for meteorological agencies to report wind speeds in miles per hour, knots, or kilometers per hour. The preferred units vary by both agency and country. In addition, various classification scales are used to describe weather events by wind speed ranges. Some of the tree-risk literature employs these scale numbers (e.g., Sinn and Wessolly 1989; Wessolly 1995; Peterson and Rebertus 1997; Wessolly and Erb 1998; Hayes 1999; Peterson 2000; Brudi 2002).

These various usages may be an obstacle to proper understanding of the tree–wind literature (Cullen 2002b), to practical tree-risk management, and to dissemination of knowledge and methods across national and cultural boundaries. The tables in this article should facilitate simple and accurate comparison.

COMPARING SCALES AND SPEEDS

A comparison of wind speed scales and wind speeds in various units of measure is presented in Table 1. The table is not intended to catalog all wind speed scales, but includes several common systems. The World Meteorological Organization provides a list of weather reporting agencies around the world (WMO, no date) that employ various systems.

Table 1.
Table 1.

Wind scales and speeds (copyright Scott Cullen 2002).

Some scales incorporate other elements of storm severity in addition to wind speed. For example, the Fujita Scale (Fujita 1987; NCDC 2001a; TTU 2002)— or Fujita-Pearson Scale—(Stormfax 2001) considers the width and length of tornado damage paths; and the Dolan-Davis Northeaster Storm Scale (Dolan and Davis 1992) considers the “storm surge” in coastal water bodies. A variety of scales are catalogued by the Natural Hazards Research Centre (2001). These scales may be useful in assessing risks of tree damage in particular locales.

TREES AS WIND SPEED INDICATORS

A number of scales have been developed to use tree movement or deformation as an indication of current or experienced wind speed.

Tree Movement and Damage

Historically, the Beaufort Scale was developed to scale wind speeds over water and describe wind effects that could be observed by mariners. The scale has been adjusted for use on land, including description of wind effects on trees. The Fujita Tornado Scale and Safffir-Simpson Hurricane Scale (NWS, no date–b; Simpson and Riehl 1981; NCDC 2001b) use tree damage as an index of wind speeds. These effects are presented in Table 2. Rating damage using the Fujita Scale has been characterized as “highly subjective and variable” (Edwards and Harmon, no date; Doswell and Burgess 1988).

Table 2.
Table 2.

Wind speeds and trees (compiled by Scott Cullen 2002).

Deformation of Trees

In chronically windy locations, wind can also affect tree growth resulting in permanent deformation. Robertson (1987) notes that a number of investigators have developed indices of deformation related to wind speeds. These indices include the Griggs-Putnam index (Putnam 1948) for North American conifers; the Barsch index (Barsch 1963) for European broadleaves; and Yoshino (1975) and Yoshino et al. (1976) for European and Japanese trees. Koeppl (1982) reports that the Griggs-Putnam index was further developed to scale deformation against wind characteristics including mean annual wind speed, mean growing season wind speed, mean nongrowing season wind speed, and percentage of winds from prevailing direction. The predictive reliability of these indices is not without critics (Hennessey 1980).

Other studies of tree deformation by chronic wind include those by Cordero (1999), Musselman et al. (1990), and Noguchi (1979, 1992).

LITERATURE CITED

  1. ↵
    1. Barsch, Dietrich
    . 1963. Wind, baumform und landschaft / Dietrich Barsch, in Studien zum problem der deformation von baumkronen durch wind. Freiburger Geographische Hefte H1 (Albert-Ludwigs-Universitaet, Geograph. Institut 1, Freiburg).
  2. Bureau of Meteorology-Australia (BoM-AU). 2001. Cyclone Severity Categories. http://www.bom.gov.au/info/cyclone/#CycloneSeverityCategories (accessed 7/24/02).
  3. ↵
    1. Smiley, E. Thomas, and
    2. Kim D. Coder
    1. Brudi, Erk
    . 2002. Trees and statics: An introduction. In Smiley, E. Thomas, and Kim D. Coder (Eds.). Proceedings of the Tree Biomechanics Conference, Savannah, GA. International Society of Arboriculture, Champaign, IL (in press).
  4. ↵
    1. Cordero, Roberto A.
    1999. Ecophysiology of Cecropia schreberiana saplings in two wind regimes in an elfin cloud forest: growth, gas exchange, architecture and stem biomechanics. Tree Physiol. 19(3):153–163.
    OpenUrlCrossRefPubMed
  5. ↵
    1. Smiley, E. Thomas, and
    2. Kim D. Coder
    1. Cullen, Scott
    . 2002a. Guying a large tree: Decision making and design (the Bedford protocol). In Smiley, E. Thomas, and Kim D. Coder (Eds.). Proceedings of the Tree Biomechanics Conference, Savannah, GA. International Society of Arboriculture, Champaign, IL (in press).
  6. ↵
    1. Cullen, Scott
    . 2002b. Trees and wind: A bibliography for tree care professionals. J. Arboric. 28(1):41–51. http://joa.isa-arbor.com/request.asp?JournalID=1&ArticleID=25&Type=1 (accessed 7/24/02).
    OpenUrl
  7. ↵
    1. Dolan, R., and
    2. R.E. Davis
    . 1992. Rating northeasters. Mariners Weather Log 36(1):4–11. (Cited in Hilton Head Flood Hazard Mitigation Plan. 1995. Town of Hilton Head, Hilton Head, SC. http://www.ci.hilton-head-island.sc.us/projects/flood/e.html (accessed 7/24/02).
    OpenUrl
  8. ↵
    1. Doswell, C.A., and
    2. D.W. Burgess
    , 1988: On some issues of United States tornado climatology. Monthly Weather Review 116:495–501.
    OpenUrl
    1. Edwards, Roger, and
    2. D. Greg Harmon
    . No date. Lubbock F-Scale Exercise on Spencer, SD Tornado Damage. Storm Prediction Center, NOAA, Norman, OK. http://www.spc.noaa.gov/misc/spencer/spenf_ex.htm (accessed 7/31/02).
  10. ↵
    1. Fujita, T. Theodore
    . 1987. U.S. Tornadoes, Part 1: 70-Year Statistics. Satellite and Mesometeorology Research Project (SMRP), Research Paper Number 218. University of Chicago. 122 pp.
  11. ↵
    1. Hayes
    , Ed. 1999. Patterns of tree failure. Tree Care Indus. X(4):37–42.
    OpenUrl
  12. ↵
    1. Hennessey, J.P.
    1980. A critique of “trees as a local climatic indicator.” J. Appl. Meteorol. 19:1020–1023.
    OpenUrl
  13. Hong Kong Observatory. 1999a. Beaufort Wind Scale. http://www.weather.gov.hk/education/article/009beaufort.htm (accessed 7/25/02)
  14. Hong Kong Observatory. 1999b. Classification of Tropical Cyclones. http://www.weather.gov.hk/informtc/class.htm (accessed 7/52/02).
  15. ↵
    1. Koeppl, Gerald. W.
    1982. Wind characteristics and turbine siting, Chapter 2 in Part 2. In Putnam’s Power from the Wind (2nd ed.). Van Nostrand Reinhold, New York, NY. 470 pp.
    1. Landsea, Christopher W.
    2000a. How are Atlantic hurricanes ranked? Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, FL. (Citing Simpson, R.H., and H. Riehl. 1981. The Hurricane and Its Impact. Louisiana State University Press, Baton Rouge, LA. 398 pp.) http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqD.html#D1 (accessed 7/25/02).
    1. Landsea, Christopher W.
    2000b. How do I convert from mph to knots and m/s? Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, FL. http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqD.html#D4 (accessed 7/25/02).
    1. Landsea, Christopher W.
    2000c. What is a super typhoon? Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, FL. (Citing U.S. Joint Typhoon Warning Center, Guam). http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqA.html#A3 (accessed 7/25/02)
  19. ↵
    1. Musselman, R.C.,
    2. G.L Wooldridge,
    3. D.G. Fox, and
    4. B.H. Connell
    . 1990. Using wind-deformed conifers to measure wind patterns in alpine transition at GLEES, pp 80–85. In Schmidt, W.C., and K.J. McDonald (Compilers). Proceedings— Symposium on Whitebark Pine Ecosystems: Ecology and Management of a High-Mountain Resource, Bozeman, Montana, March 29-31, 1989. Intermountain Station General Technical Report INT-270.
  20. National Institute of Science and Technology (NIST). No date. Guide for the Use of the International System of Units (SI)—Velocity. http://physics.nist.gov/Pubs/SP811/appenB8.html (accessed 7/25/02).
  21. National Climate Data Center (NCDC). 2000. Knots to Miles per Hour Conversion Chart. NOAA, Asheville, NC. http://www.ncdc.noaa.gov/ol/climate/conversion/windchart.html (accessed 7/25/02).
  22. ↵
    National Climate Data Center (NCDC). 2001a. The Fujita Tornado Scale. NOAA, Asheville, NC. http://www.ncdc.noaa.gov/ol/satellite/satelliteseye/educational/fujita.html (accessed 7/25/02).
  23. ↵
    National Climate Data Center (NCDC). 2001b. The Saffir/ Simpson Hurricane Scale. NOAA, Asheville, NC. http://lwf.ncdc.noaa.gov/oa/satellite/satelliteseye/educational/saffir.html (accessed 7/25/02).
  24. National Weather Service (NWS). 1999. Modified Saffir/Simpson hurricane scale (SSHS) for the northwest Pacific (Appendix A, NWS Operations Manual W/OM12 8/19/99), NOAA, Silver Spring, MD. http://www.nws.noaa.gov/wsom/manual/archives/NC419903.HTML (accessed 7/25/02).
  25. National Weather Service (NWS). No date–a. Saffir/Simpson Hurricane Scale, NOAA, Silver Spring, MD. http://www.nws.noaa.gov/er/box/Saffir.html (accessed 7/25/02).
  26. National Weather Service (NWS). No date–b. Beaufort Wind Scale. Storm Prediction Center, NOAA, Norman, OK. http://www.spc.noaa.gov/faq/tornado/beaufort.html (accessed 7/25/02).
  27. ↵
    Natural Hazards Research Centre. 2001. Damage Scales. Division of Environmental & Life Sciences, Macquarie University, Sidney, NSW, Australia. http://www.es.mq.edu.au/NHRC/web/scales/scalesindes.htm (accessed 7/25/02).
  28. Navy Guam Weather Watch. No Date. Tropical Cyclones. http://www.guam.navy.mil/weather.htm (accessed 7/25/02).
  29. ↵
    1. Noguchi, Y.
    1992. Vegetation asymmetry in Hawaii under the trade wind regime. J. Veg. Sci. 3(2):223 ff.
    OpenUrl
  30. ↵
    1. Noguchi, Y.
    1979. Deformation of trees in Hawaii and its relation to wind. J. Ecol. 67:611–628.
    OpenUrl
  31. ↵
    1. Peterson, C.J.
    2000. Damage and recovery of tree species after two different tornadoes in the same old growth forest: A comparison of infrequent wind disturbances. For. Ecol. Manage. 135(1-3):237–252.
    OpenUrl
  32. ↵
    1. Peterson, C.J., and
    2. A. J.Rebertus
    . 1997. Tornado damage and initial recovery in three adjacent, lowland temperate forests in Missouri. J. Veg. Sci. 8(4):559–564.
    OpenUrl
  33. ↵
    1. Putnam, Palmer Cosslett
    . 1948. Power from the Wind. Van Nostrand-Reinhold, New York, NY. 223 pp.
  34. ↵
    1. Robertson, Alexander
    . 1987. The use of trees to study wind. Arboric. J. 11:127–143.
    OpenUrl
  35. ↵
    1. Simpson, R.H., and
    2. H. Riehl
    . 1981. The Hurricane and Its Impact. Louisiana State University Press, Baton Rouge, LA. 398 pp.
  36. ↵
    1. Sinn, Günter, and
    2. Lothar Wessolly
    . 1989. A contribution to the proper assessment of the strength and stability of trees. Arboric. J. 13(1):45–65.
    OpenUrl
  37. ↵
    Stormfax. 2001. Fujita-Pearson Tornado Scale. Stormfax® Weather Almanac. http://www.stormfax.com/fujita.htm (accessed 7/25/02).
  38. ↵
    Texas Tech University (TTU). 2002. Fujita Tornado Damage Scale. Wind Engineering Research Center, Texas Tech University, Lubbock, TX. http://www.spc.noaa.gov/faq/tornado/f-scale.html (accessed 7/25/02).
  39. ↵
    1. Wessolly, Lothar
    . 1995. Fracture diagnosis of trees, part 3: Boring is no way for reliable fracture diagnosis (including literature citations for parts 1, 2, and 3). Stadt und Grün 9:635–640.
    OpenUrl
  40. ↵
    1. Wessolly, Lothar, and
    2. M. Erb
    . 1998. Handbüch der Baumstatik und Baumkontrolle (in German). Patzer-Verlag, Berlin, Germany. 270 pp.
  41. World Meteorological Organization (WMO). No date. National Weather Services Affected by Tropical Cyclones. WMO, Geneva. http://www.wmo.ch/web/www/TCP/National%20Warnings.htm (accessed 7/25/02).
  42. ↵
    1. Yoshino, M.M.
    1. Yoshino, M.M.,
    2. M.T. Yoshino,
    3. M. Yoshimura,
    4. K. Mitsui,
    5. K. Urushibara,
    6. S. Ueda,
    7. M. Owada, and
    8. K. Nakamra
    . 1976. Bora regions as revealed by wind-shaped trees on the Adriatic Coast, pp 59–71. In Yoshino, M.M. (Ed.). Local Wind Bora. University of Tokyo Press, Tokyo, Japan.
  43. ↵
    1. Yoshino, M.M.
    1975. Wind-shaped trees, Chapter 6.1.3, pp 445—458. In Climate in a Small Area. University of Tokyo Press, Tokyo, Japan.
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Technical Note: Trees and Wind: Wind Scales and Speeds
Scott Cullen
Arboriculture & Urban Forestry (AUF) Sep 2002, 28 (5) 237-242; DOI: 10.48044/jauf.2002.036
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