Volume 13, Issue 1 (2009)                   MJSP 2009, 13(1): 219-245 | Back to browse issues page

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1- Tarbiat Modares University, Tehran, Iran
2- . Iranian Meteorological Organization, Tehran, Iran
3- Ph.D. Candidate of Tarbiat Modares University, Tehran, Iran
4- Faculty member of Atmospheric and Meteorological Research Center (ASMERC)
Abstract:   (8246 Views)
The NCEP/NCAR monthly mean reanalysis data have been used to investigate the temporal and spatial variations of subtropical anticyclones over the Asia-Africa. The geopotential height and zonal and meridional wind components of 1000, 500, 200 and 100 hPa in a 30-year period (1971-2000) have been employed to determine the geographical characteristics, frequency and ridgeline of subtropical anticyclone in a domain of 60 -120 from April to October. The results revealed that there is an obvious difference about the location of subtropical anticyclones at lower, middle and upper levels. While Iranian anticyclone has been located in both middle and upper levels of troposphere, the Azores high, the Northwest African anticyclone, the Saudi Arabia anticyclone and the Tibetan anticyclone have just seen at lower, middle and upper levels of troposphere, respectively. The summertime geographical pattern of anticyclone center at 1000, 500, 200 and 100 hPa showed one mode (east of Atlantic Ocean), three mode (northwest Africa-Iran-Saudi Arabia), dispersed(from south china to west of Iran) and bimodal (Tibetan plateau-Iranian plateau) of distribution, respectively. In all levels, the maximum latitude of the ridgeline of subtropical anticyclone has related to august, which have been located over the northern flank of Tibetan plateau at 500 hPa, a wide region from the east to west of Asia at 200 hPa and Iran at 100 hPa. The most latitudinal jumping of ridgeline was from June to July, which has been reaching to 10 degrees along some longitudes.
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Received: 2007/07/1 | Accepted: 2008/01/16 | Published: 2010/02/16

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