Local convergence zones or discontinuous lines in the Taklimakan Desert, Northwest China

In order to study convergence zones or discontinuous lines formed locally in the Taklimakan Desert, we analyzed available MODIS images onboad TERRA or AQUA satellite for ten cases: 29 March 2002, 14 April 2002; 2 January 2003; 21 April 2003; 26 March 2004; 28 April 2004; 30 January 2005; 25 June 2005; 3 December 2005; and 26 July 2006. We used weather maps published by the Japan Meteorological Agency for the Asia and Pacific region at 500 hPa, 700 hPa and 850 hPa, at 00Z and 12Z to analyze the meteorological conditions occurring in each case. We estimated the positions of air streams, convergence zones or discontinuous lines between them, and thermal conditions on the maps and confirmed the presence of cumulus and cumulonimbus clouds through satellite images in particular. After a review of previous studies, this paper introduced the results of the present study. Closed warm areas in the Taklimakan Desert and on the Tibetan Plateau and local convergence zones or discontinuous lines in the Taklimakan Desert were discussed together with their diurnal changes, using composite maps of the ten cases. Along the long axis of the desert the convergence zones or discontinuous lines normally extend 70-80 km in a west-east direction, but are suspected to exceed 100 km in extreme cases. On the other hand, the convergence zones or discontinuous lines extending in a north-south direction on the southern fringe of the desert have a length of 40-60 km. The closed warm areas show clear diurnal changes, but they were not detected at the 500 hPa level. An example of a clear convergence zone running in a north-south direction on 26 July 2006 was presented in detail with corresponding satellite images.