Associated Professor of Geography, Yazd University, Yazd, Iran
Abstract: (13813 Views)
One of the natural disasters causing many damages in dry and desert areas of the world and especially in the Yazd region of Iran, is strong winds and storms. This region (Yazd), due to it is geographical situation and climatic conditions, is always subject to strong winds and dust storms. Therefore, understanding the storms and strong winds regime, in order to reduce the destructive effects of this phenomenon, especially in stabilizing the running sands, is necessary.
This study was accomplished using the data of horizontal vision, speed and direction of wind, relative humidity, temperature, pressure, cloud and dust event in Yazd and Kerman synoptic stations, as well as the atmosphere data of the above stations, and the synoptic maps during statistical period between 1983-2003.
The results of the study showed that more than 77 percent of strong winds in the area blow from 2500 to 3300, and its speed is between 15-29 m/sec during the fluctuation. These strong winds blow in the afternoons. The blow of dominant winds is from North -West and West. More than 5 percent of storms and strong winds in this region occur in Apirl and May.
In the begining of the hot period of the year and changing of the season, the atmospheric instability and the dust storms increase in the region. The main reason of this phenomena is the intensive winds that occur by the fast changes of the temperature and pressure in this time. Passing of a low pressure system with cold and dry front from the West-North Western along with the presence of trough in the 500 and 850 hpa levels, and also the local instabilities are the most important reasons of these strong winds in this region.
Received: 2007/05/8 | Accepted: 2008/10/30 | Published: 2010/10/13