Advertisement

Climate Dynamics

, Volume 53, Issue 5–6, pp 3691–3701 | Cite as

Study of tropical tropospheric and lower stratospheric zonal wind variability in the context of dry and wet Indian summer monsoon years

  • V. K. MiniEmail author
  • K. S. Hosalikar
  • N. Haridasan
  • Kunal Kausik
Article

Abstract

This paper describes the comparative study on some features of the tropospheric and lower stratospheric circulation over the tropical Indian region during the monsoon season in the context of deficient and excess monsoon (dry and wet) years. The monthly mean of zonal wind component are computed directly with NCEP reanalysis data for the main rainy season of June–September. The composite anomalies of zonal wind circulation for monsoon season in four meteorologically important regions of lower atmosphere viz., lower troposphere, middle troposphere, upper troposphere and lower stratosphere in respect of wet and dry monsoon years were calculated and compared. The results of our analysis show major contrasts between the characteristics of winds of tropical troposphere and lower stratosphere over Indian region during the two scenarios. In the dry years, the troposphere and lower stratosphere are characterized by weaker wind flows in comparison with the normal flow of low level jet (LLJ) and tropical easterly jet (TEJ) streams . The observed weak LLJ and TEJ support the rainfall deficit in dry years. In contrast, during the wet years, the troposphere is dominated by stronger westerly flows at lower and middle tropospheric levels in concomitant with stronger easterlies in the upper troposphere and lower stratosphere. The long term variability of zonal winds averaged between 20°N and 20°S shows decreasing trend in the absolute values in speed during 1981 to 2010. Over the period of study, both tropical westerlies and easterlies and also jet streams have weakened. The results from this study serve as bases for further work on the tropospheric circulation features over the tropical Indian region for an enhanced understanding of the regional climate.

Keywords

Zonal wind Tropical troposphere Lower stratosphere Excess monsoon year Deficient monsoon year 

Notes

References

  1. Findlater JA (1969) Major low-level air current near the Indian Ocean during the northern summer. Q J R Meteorol Soc 95:362–380CrossRefGoogle Scholar
  2. Hastenrath S (1985) Climate and circulation of the tropics. D. Reidel, DordrechtCrossRefGoogle Scholar
  3. Joseph PV, Raman PL (1966) Existence of low-level westerly jet stream over peninsular India during July. Indian J Meteorol Hydrol Geophys 17:407–410Google Scholar
  4. Joseph PV, Sijikumar S (2004) Intraseasonal variability of the low-level jet stream of the Asian summer monsoon. Am Meteorol Soc 17:1449–1458Google Scholar
  5. Kalnay E et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
  6. Kanamitsu M, Krishnamurthy TN (1978) Northern summer tropical circulation during drought and normal rainfall months. Mon Weather Rev 106:331–347CrossRefGoogle Scholar
  7. Koteswaram P (1958) The easterly jet streams in the tropics. Tellus 10:43–57CrossRefGoogle Scholar
  8. Krishnamurti TN, Astling E, Kanamits M (1975) 200 mb wind filed in June and August 1972, Rep. 75-2. Dept. of Meteorology, Florida State University, p 115Google Scholar
  9. Krishnamurti TN, Bedi HS, Subramaniam M (1989) The summer monsoon of 1987. J Clim 2(4):321–340CrossRefGoogle Scholar
  10. Murakami T (1974) Atmospheric response to heat sources during July, UHMET 74-04. Dept. of meteorology, University of Hawaii, p 50Google Scholar
  11. Rajeevan M (1993) Upper tropospheric circulation and thermal anomalies over Central Asia associated with major drought and flood in India. Curr Sci 64:244–247Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.India Meteorological DepartmentGoaIndia
  2. 2.India Meteorological DepartmentMumbaiIndia

Personalised recommendations