Investigating changes spatial pattern internal dust source in recent decades in Khuzestan province

Dusting phenomena are among the most serious environmental problems in certain areas of the world. Most of the dust in the atmosphere is due to the origin of fine particles, and these fine particles are more prevalent in the arid and semi-arid regions of the world. In general, a dust storm is a heavy wind that carries sand particles in the air and transfers them from one place to another. The diameter of the particles of these grains has a direct relation with the wind speed, so winds can transport more coarse material faster and vice versa. In examining the scientific sources available in the field of dust, it can be concluded that so far there has been a lot of research in this regard. And in most of these studies, the transmission, publication, synoptic causes and the destructive effects of this phenomenon are expressed. In this research, we try to investigate and analyze the spatial pattern of dust and changes in spatial displacement of these patterns during different periods.

Materials & Methods
The purpose of this study was to investigate and analyze spatial Autocorrelation of Khuzestan province over recent decades. For this purpose, data collected from 20 synoptic stations on a daily basis from from 1986 to 2016 were obtained from the country's Meteorological Organization. In order to investigate more accurate changes of dust, the spatial variations of Dust cores were investigated and analyzed in six periods of 5 years ((1990-86, 1995-1991, 2000-1996, 2005-2001, 2010-2006, 2016-2011) and three decades (1995-1986, 2005 1996, 2006, 2016-2006) was analyzed. In order to obtain a general view of the dusts of Khuzestan province, some descriptive characteristics of the dusts of Khuzestan province were first studied and analyzed. The Alexander's method was then used to identify the dominant mutations in the Khuzestan circle. In this study, two parameters of Moran (I) and GI * index have been used to study and analyze the spatial pattern of dusts of Khuzestan province.

Discussion of Results

The results of the frequency distribution of dust in different periods showed that in the first period (1986-1986), the Core of the occurrence of the summits was observed in the central parts of Khuzestan province and south, while during the second period Core events It is formed in the form of spots in northern parts of the province. In the third period (1996-1996), the core of dusts are almost the same as in the first period, with the exception that during this period the severity of the events has decreased. Distribution of dust events in the fourth period (2005-2001) has almost reached the same level as the second period, with the exception that the aggregate core have tended to be closer to the border areas of Iran and Iraq. In the fifth period (2010 - 2006) and the sixth period (2016-2011), the frequency of the occurrence of storms in comparison to previous periods, in addition to being increased, has been observed more in the border areas of Iran and Iraq. The results of spatial pattern changes in the dusts of Khuzestan province showed that the positive spatial Autocorrelation pattern on the districts of the province was more dispersed in the first three periods more sporadically, especially in central parts, southern parts and insignificant parts of Northern Province. Since the third period, the spatial variations of the dust patterns of Khuzestan province have been quite evident. The status of the spatial autocorrelation pattern of dust on the annual scale is approximately the same as the pattern governing the dust of the fifth and sixth periods. In the annual scale, the pattern of the dusty areas of the province in the border areas and parts of Ahwaz has formed a high cluster pattern and the southeastern regions and parts of the north of the province, especially Hossein, have a low cluster pattern (negative spatial autocorrelation pattern). As a result of recent periods, the pattern of positive spatial Autocorrelation patterns is more concentrated in the border areas of Iran and Iraq and southern parts of Khuzestan province. The low cluster pattern (negative spatial Autocorrelation pattern) is more focused along the Zagar Mountains and the southeastern provinces of the province.

Conclusions
The dusty phenomenon is one of the most important climatic events in many parts of the world, especially in countries in the dry and dry land, especially in the subtropical regions. In this study, the spatial pattern core of dust the Khuzestan province has been investigated. Then, the spatial autocorrelation pattern was used from two indicators of the Hot Spot Index (GI *) and Moran (I) or Moran Index. The results of this study showed that the dust of Khuzestan province were more severe in the western and southern parts of the country. On the other hand, since the third period, the incident has increased dramatically over recent periods. The results of the analysis of spatial autocorrelations hotspot indicates that during the first three core dust for spots in parts of central, northern (part of Safiabad) and parts of South and West Khuzestan province scattered. The low cluster pattern (negative spatial autocorrelations pattern) is further concentrated along the Zagros Mountains and the southeastern provinces of the province. So, we can say that as far as recent periods are farther away from the border regions, the severity of positive spatial mapping patterns is reduced and, in spite of the severity of the spatial autocorrelations pattern, is increased.