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Advances in Atmospheric Sciences

, Volume 18, Issue 5, pp 864–872 | Cite as

Local Meridional Circulation and Deserts

  • Liu Ping
  • Wu Guoxiong
  • Sun Shufen
Article

Abstract

This paper investigates the dry climatology of Sahara and Northwest China deserts from the viewpoint of local meridional circulation with Xie and Arkin rainfall dada and NCAR I NCEP reanalysis data. Results show that there are very dry centers with annual rainfall less than 50 mm over these two deserts while the rainy seasons are very different. In the south part of Sahara desert center and Northwest China desert, over 70% rainfall takes place in June, July and August (JJA). While in the north part of Sahara, rainfall mainly concentrates in December, January and February (DJF). The local biosphere-radiation mechanism proposed by Charney cannot explain the climatology of such very dry centers. Neither can the monsoon-desert mechanism proposed by Rodwell and Hoskins do for the strongest descent center is much more northward than the driest center over Sahara in JJA. From the viewpoint of local meridional circulation, the dryness climatology of Sahara and Northwest China deserts is investigated and compared. It is shown that in DJF, descent of local meridional circulation dominates the two deserts and very dry climate is unavoidable although the relative wet season is weak over the northern part of Sahara due to Mediterranean climate. While in JJA, there is ascent over the two deserts especially over Northwest China. Such ascent can explain the rainy season in south part of Sahara and Northwest China deserts. However, it is the local meridional circulation that takes strong and dry northerly from higher latitudes. The northerly either takes little moisture to the centers or prevents deep and strong convection over the centers. Such local meridional circulation leads to the dry climatology over the two deserts.

Key words

Deserts Local meridional circulation 

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References

  1. Charney, J. G., 1975: Dynamics of deserts and drought in the Sahel. Quart. J. Roy. Meteor. Soc., 101, 193–202.CrossRefGoogle Scholar
  2. Rodwell, M. J., and B. J. Hoskins, 1996: Monsoons and dynamics of deserts. Quart. J. Roy. Meteor. Soc., 122, 1385–1404.CrossRefGoogle Scholar
  3. Xie, P., and P. A. Arkin, 1997: Global precipitation: A 17-year monthly analysis based upon gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78, 2539–2558.CrossRefGoogle Scholar
  4. Xue, Y. K., 1996: The impact of desertification in the Mongolian and the Inner Mongolian grassland on the regional climate. J. Climate, 9, 2173–2189.CrossRefGoogle Scholar

Copyright information

© Advances in Atmospheric Sciences 2001

Authors and Affiliations

  • Liu Ping
    • 1
  • Wu Guoxiong
    • 1
  • Sun Shufen
    • 1
  1. 1.LASG, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina

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