Analysis of the dust event in the recent decade (2002- 2012): Mashhad case study

Dust is one of the atmospheric phenomena with undesired bio-environmental outcomes. Due to Iran’s geographical situation in arid and semi-arid parts of the world, this country is repeatedly exposed to synoptic and local dust systems. This study investigates the initiation conditions and the origin of dust systems of Mashhad during a statistical decade (2002- 22012). The results of statistical analysis show that summer, especially June with 29 days has the highest abundance of the dust event phenomenon in Mashhad. Statistics has shown a decreasing trend of this phenomenon in recent years. Of course it is important to mention that this event has increased from 2012 to the previous year, i.e. 2011. In addition, the abundance of the days of the dust event phenomenon with intra-regional and local origin is higher than its occurrence with extra-regional one. Finally in order to synoptically analyze this phenomenon, the effective factors on this atmospheric phenomenon were investigated typically with the help of the maps received from the weather forecast site. For the analysis, two waves were selected due to the dispersion of the area .and its deployment in the region. The dates of the phenomenon were selected as July 9th 2009 as the extra-regional factor and March 15th 2008 as the intra-regional one. Results show that in July 9th for the extra-regional factor, there was a fairly moderate atmosphere on the region, while on the surrounding regions, the placement of a low-pressure atmosphere, reinforcement of the instability conditions and cutting the upper-layer winds has led to the weather calmness and therefore the occurrence of the dust phenomenon and its placement on the region. By investigating the maps of the atmosphere’s various surfaces on March 15th with the intra-regional factor, there were different conditions in comparison with the July 9th. At the time of the occurrence of the phenomenon on March 15th, the conditions were instable on various surfaces from the Earth to the over-atmosphere surfaces, while there was a fairly moderate atmosphere around the regions. This instability on the regions leads to the air movement and the region’s aridness makes local dust.

کلیدواژه ها:

Dust ، Statistical analyses ، Synoptic maps ، NOAA website ، Mashhad