Wind of 120 days

The 120-day wind or wind of 120 days (Persian: باد صد و بیست روزه, "one hundred and twenty days wind") is a strong summer wind occurring from late May to late September in the east and southeast of the Iranian Plateau,[1] particularly the Sistan Basin. It is so called because it lasts for four months.[2] The typical wind speed is 30–40 kilometres per hour (19–25 mph) or less, but it can occasionally exceed 100–110 kilometres per hour (60–70 mph).[1] Strong speeds are caused by the topography surrounding the region.[3] The wind moves fairly consistently south-to-southeastward;[4][3] along with the shamal, it is one of two well-known winds in Iran.[4]

During the "depression of Sistan", the four months when the wind is strongest, winds from northern Afghanistan and from the deserts of eastern Iran and western Afghanistan combine, resulting in accelerated high-pressure winds blowing from the central Iranian deserts toward Sistan and Baluchestan Province.[4] The 120-day wind affects all of the Helmand Basin, but Sistan receives stronger winds as they intensify between the mountains of Iran and Afghanistan.[5] The wind is relatively hot and carries abrasive sand particles.[6] It causes evaporation in the Sistan Basin, contributing to drought in the region.[7]

  1. ^ a b de Planhol, X. (19 August 2011). "bād (1)". Encyclopaedia Iranica. Vol. 3. pp. 349–350. ISSN 2330-4804. Retrieved 22 October 2019.
  2. ^ Spilsbury, Louise; Spilsbury, Richard (2011). Iran. Countries Around the World. Raintree Publishers. ISBN 978-1406233490.
  3. ^ a b Cite error: The named reference atmos was invoked but never defined (see the help page).
  4. ^ a b c Ganji, M. H. (1968). "Climate". In Fisher, William Payne (ed.). The Land of Iran. The Cambridge History of Iran. Vol. 1. Cambridge: Cambridge University Press. p. 219. ISBN 978-0521069359.
  5. ^ Whitney, John W. (2006). Geology, water, and wind in the Lower Helmand Basin, Southern Afghanistan. Scientific investigations report. Reston, VA: Department of the Interior, U.S. Geological Survey. OCLC 1049741054.
  6. ^ Kheirabadi, Masoud (2009). Iran. Modern World Nations. Philadelphia, PA: Chelsea House Publishers. p. 22. ISBN 978-1438105123.
  7. ^ Mojtahed-Zadeh, Pirouz (2006). "Hydropolitics of Hirmand and Hamun". In Mojtahed-Zadeh, Pirouz (ed.). Boundary Politics and International Boundaries of Iran. Boca Raton, FL: Universal Publishers. p. 246. ISBN 978-1581129335.