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Changes in Hadley circulation: the Azores high and winter precipitation over tropical northeast Africa

  • M. J. Iqbal
  • S. U. RehmanEmail author
  • Sultan Hameed
  • M. A. Qureshi
Original Paper
  • 13 Downloads

Abstract

We present a study of changes in winter precipitation over a region in tropical northeast Africa during 1951–2015. A persistent drying trend is present in this region in addition to interannual variability. We present evidence that the changes in precipitation are primarily influenced by a strengthening of Azores high (AH) pressure. The correlation of AH pressure to changes in precipitation in tropical northeast Africa is statistically more significant than correlations between precipitation and the Arctic Oscillation (AO), the Southern Oscillation (SO), or the North Atlantic Oscillation (NAO). It is also shown that the AH pressure in winter has steadily increased in recent decades which explains the drying trend over tropical northeast Africa over the same period. The AH represents the subsiding branch of Hadley circulation over the north Atlantic sector, i.e., increasing pressure of the AH is evidence of intensification of Hadley circulation in the north Atlantic region since the 1950s.

Notes

References

  1. Bakalian F, Hameed S, Pickar R (2007) Influences of the Icelandic Low latitude on the frequency of Greenland tip jet events: implications for Irminger Sea convection. J Geophys Res 112:C04020.  https://doi.org/10.1029/2006JC003807 CrossRefGoogle Scholar
  2. Doherty OM, Riemer N, Hameed S (2008) Saharan mineral dust transport into the Caribbean: observed atmospheric controls and trends. J Geophys Res Atmos 113(D7)Google Scholar
  3. Frierson DMW (2006) Robust increases in midlatitude static stability in simulations of global warming. Geophys Res Lett 33:L24816.  https://doi.org/10.1029/2006GL027504 CrossRefGoogle Scholar
  4. Giannini A, Biasutti M, Held IM, Sobel AH (2008) A global perspective on African climate. Clim Chang 90(4):359–383CrossRefGoogle Scholar
  5. Hameed S, Piontkovski S (2004) The dominant influence of the Icelandic Low on the position of the Gulf Stream northwall. Geophys Res Lett 31:L0903CrossRefGoogle Scholar
  6. Held IM, Soden BJ (2006) Robust responses of the hydrological cycle to global warming. J Clim 19:5686–5699CrossRefGoogle Scholar
  7. Hsu DF, Wallace JM (1976) The global distribution of the annual and semiannual cycles in precipitation. Mon Weather Rev 104:1093–1101CrossRefGoogle Scholar
  8. Hu Y, Fu Q (2007) Observed poleward expansion of the Hadley circulation since 1979. Atmos Chem Phys 7:5229–5236Google Scholar
  9. Hurrell JW (1995) Decadal trend in the North Atlantic Oscillation: regional temperatures and precipitation. Science 269:676–679CrossRefGoogle Scholar
  10. Iqbal MJ, Ilyas K (2011) Influence of Icelandic Low pressure on winter precipitation variability over northern part of Indo-Pak Region. Arab J Geosci.  https://doi.org/10.1007/s12517-011-0355-y (first online published), Springer
  11. Kidson JW (1977) African rainfall and its relation on the upper air circulation. Q J R Meteorol Soc 103:441–456CrossRefGoogle Scholar
  12. Lamb PJ, Peppler RA (1987) North Atlantic Oscillation: concept and application. Bull Am Meteorol Soc 68:1218–1225CrossRefGoogle Scholar
  13. Lu J, Vecchi GA, Reichler T (2007) Expansion of the Hadley cell under global warming. Geophys Res Lett 34(6)Google Scholar
  14. McHugh MJ, Rogers JC (2001) North Atlantic oscillation influence on precipitation variability around the southeast African convergence zone. J Clim 14:3631–3642CrossRefGoogle Scholar
  15. Meehl GA, Van Loon H (1979) The seasaw in winter temperatures between Greenland and northern Europe. Part III: teleconnections with lower latitudes. Mon Weather Rev 107(9):1095–1106CrossRefGoogle Scholar
  16. Mitas CM, Clement A (2006) Recent behavior of the Hadley cell and tropical thermodynamics in climate models and reanalysis. Geophys Res Lett 33:L01810.  https://doi.org/10.1029/2005GL024406 CrossRefGoogle Scholar
  17. Nicholson SE (1981) The historical climatology of Africa. In: Wigley TML, Ingram MJ, Farmer G (eds) Climate and history. Cambridge Press, Cambridge, pp 249–270Google Scholar
  18. Nicholson SE (1996) A review of climate dynamics and climate variability in eastern Africa. In: Johnson TC, Odada E (eds) The Limnology, Climatology and Paleoclimatology of the East African Lakes. Gordon and Breach, Amsterdam, pp 25–56Google Scholar
  19. Nicholson SE (2000) The nature of rainfall variability over Africa on time scales of decades to millenia. Glob Planet Chang 26:137–158CrossRefGoogle Scholar
  20. Okumura Y, Xie SP, Numaguti A, Tanimoto Y (2001) Tropical Atlantic air-sea interaction and its influence on the NAO. Geophys Res Lett 28(8):1507–1510CrossRefGoogle Scholar
  21. Riemer R, Doherty OM, Hameed S (2006) On the variability of African dust transport across the Atlantic. Geophys Res Lett 33:L13814CrossRefGoogle Scholar
  22. Rossby CG (1939) Relation between variations in the intensity of the zonal circulation of the atmosphere and the displacements of the semi-permanent centers of action. J Mar Res 2:38–55CrossRefGoogle Scholar
  23. Seager R, Ting M, Held I, Kushnir Y, Lu J, Vecchi G et al (2007) Model projections of an imminent transition to a more arid climate in southwestern North America. Science 316(5828):1181–1184CrossRefGoogle Scholar
  24. Taylor GT, Muller-Karger F, Thunell RC, Scranton MI, Astor Y, Varela R, Ghinaglia LT, Lorenzoni L, Fanning KA, Hameed S, Doherty O (2012) Ecosystem responses in the southern Caribbean Sea to global climate change. Proc Natl Acad Sci 109:19315–19320CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  • M. J. Iqbal
    • 1
  • S. U. Rehman
    • 2
    Email author
  • Sultan Hameed
    • 3
  • M. A. Qureshi
    • 1
  1. 1.Institute of Space and Planetary AstrophysicsUniversity of KarachiKarachiPakistan
  2. 2.Department of MathematicsUniversity of KarachiKarachiPakistan
  3. 3.School of Marine and Atmospheric SciencesStony Brook UniversityStony BrookUSA

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