Climatology and classification
of Spring Saharan cyclone tracks
A. Hannachi • A. Awad • K. Ammar
Climate Dynamics;Aug 2011, Volume 37, Issue 3-4, pp
473-491
DOI 10.1007/s00382-010-0941-9
Received: 22 December 2009 / Accepted : 26 October 2010 :
Springer-Verlag 2010 :
Abstract :
Spring Saharan cyclones constitute a dominant feature of the not-well-explored Saharan region. In this manuscript, a climatological analysis and classification of Saharan cyclone tracks are presented using 6-hourly NCEP/NCAR sea level pressure (SLP) reanalyses over the Sahara (10°W–50°E, 20°N–50°N) for the Spring (March–April–May) season over the period 1958–2006. A simple tracking procedure based on following SLP minima is used to construct around 640 Spring Saharan cyclone tracks. Saharan cyclones are found to be short-lived compared to their extratropical counterparts with an e-folding time of about 3 days. The lee side of the west Atlas mountain is found to be the main cyclogenetic region for Spring Saharan cyclones. Central Iraq is identified as the main cyclolytic area. A subjective procedure is used next to classify the cyclone tracks where six clusters are identified. Among these clusters the Western Atlas–Asia Minor is the largest and most stretched, whereas Algerian Sahara–Asia Minor is composed of the most long-lived tracks. Upper level flow associated with the tracks has also been examined and the role of large scale baroclinicity in the growth of Saharan cyclones is discussed.
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