Time evaluating of dust phenomenon in Alborz and Qazvin provinces

Statistical investigation of dust phenomenon in Alborz and Qazvin provinces
Introduction
Dust is a phenomenon that mainly occurs on arid and semiarid regions due to the high wind speed and its turbulence on soil surface of without any cover and talent to erosion (Khoshhal Dastjerdi et al., 2012). Goudie et al. (2009) point out that Sahara Desert are the strongest sources of global dust in West Africa and western China. Kumar et al. (2015) investigated three major dust events in 2010 that occurred in northern India during the monsoon season, by land measurements, satellite, and model estimation. The results showed that all dust storms originating from the desert or transported from it were affected by favorable conditions. In this paper, the annual and monthly frequency of dust phenomena in Qazvin and Alborz provinces has been studied during the statistical period in order to minimize the damage caused by this phenomenon using its results.
Material & methods
Study area
Alborz province is located in the middle part of the Alborz Mountains that is adjacent to the north of Mazandaran province and south with the central province of the east with Tehran province and west to Qazvin province.
Methodology
For statistical study of dust was collected dust daily data in special codes for period of 15 years (2000-2014) from 7 selected stations in study area with suitable statistical period from meteorological organization that were processed using statistical methods. The extraction of days with dust was carried out using weather codes of 06 and 07 using MATLAB software. code of 06 is the dust is suspended in the air that is caused by soil and sand storm from distant points to the station and code of 07 is the dust or sands that raises by wind at station or near it in observation time. In this research, monthly and annual frequency of days with dust with visibility less than 10 km was investigated and separated with regard to codes of 06 and 07.
Discussion of result
The annual survey of dust phenomena
The annual frequency of occurrence of days with dust showed that has occurred 549 days with dust according to codes of 06 and 07 for selected station in Alborz and Qazvin provinces. Karaj and Qazvin stations with 169 days and 115 days had the most day with dust respectively. Karaj station had most dust with 25 days in 2012 and 24 days in 2014 and there not have been dust in 2001 that annual average of dust was 11 days. Qazvin station had the most dust day with dust with 23 days in 2011 and there was not dust in 2002 and 2007 and the annual average of dust was 7 days.
The frequency of days with dust with breakdown of 06 and 07 codes showed that the most days with dust according to 06 code has been occurred with 104 days at Karaj station and the lowest dust events have occurred with 36 days at Avaj station. Karaj station has been the most dust events with 22 days in 2014 and the annual average of dust days was 7 days. Qazvin station totally had 91 days dust events that occurred the most dust occurrence with 22 days in 2011 and there was not dust in 2002, 2004 and 2007. Taleghan station had the most dust events with frequency of 19 days in 2012 and the lowest dust events with 6 days in 2014. Also, the average of days with dust was 11 days that was higher than other stations. Karaj and Qazvin station had the most frequency of dust events with 69 days and 27 days respectively.
The annual survey of dust phenomena
The monthly dust survey showed that have been occurred the most frequency of dust events in May with 116s and June with 115 days in selected stations in the statistical period of 2000 to 2014. May had the most dust with 32 days at Qazvin stations and June had the most dust with 30 days at Karaj station. Then, April with 79 days and July with 70 days had the most dust respectively that in April, Qazvin station had the most with 18 days and Karaj station had the most dust with 23 days and November and December had the lowest dust with 9 days. The monthly survey of dust phenomenon according to 06 code showed that May with 90 events of dust and June with 85 events of dust had the most frequency of dust events at selected stations in the study period respectively. The monthly survey according to 07 code showed that June and October with 15 incidences had the most dust that with regard to it Karaj station with frequency of 13 days in June and 7 days in October had the most dust. December and November with 1 and 2 days had the lowest frequency of dust occurrence respectively, and January according to 07 code had not dust during statistical period.
Conclusion
The study of annual frequency of days with dust according to 06 code showed that the most days with dust occurred at Karaj station and the lowest dust events occurred at Avaj station that Karaj station had the most dust incidence with 22 days in 2014. According to 07 code, Karaj and Qazvin stations had the most events of dust and Buin Zahra and Avaj had the lowest events of dust respectively. With the monthly investigation of dust based on 06 code was found May and June had the most frequency of dust event that with regard to it, Qazvin station had the highest events in May with 30 days and June with 19 days. According to 07 code June and October had the highest incidence of dust that with regard to it, Karaj station had the most dust with 13 days frequency in June and 7 days in October. In general, based on the results, it was found that in the study area, with the onset of the spring season and the warm period followed by the summer season, the frequency of days with dust has increased, which can be due to increased hours of daily sunlight, superheating, and also There are some local instabilities. Another important factor is the passage of waves of the western masses from the deserts of neighboring countries, which, due to the dryness of the air flow and desert environment in those regions, causes dust and its penetration into the central parts of Iran. Movahedi et al. (2014) monitored the dust-related climate-related phenomena according to dust-weather codes for Iranian cities, and concluded that the dust phenomenon with the 06-meteorological code in western Iran has a maximum incidence, and in the season Summer is the highest and in the fall, is the lowest amount of dust. Also, incidence of dust occurred according to 07 code in the befor afternoon in the east of the Iran and occurred in the southeast and the coastal area of Oman sea in the late afternoon. Therefore, the findings of this study are consistent with some of the results of this study. According to the results obtained, it can be concluded that by examining the time and place of the occurrence of dust phenomena, it is possible to reduce the many damage caused by this phenomenon that threatens the environment and human health. It is very difficult to control dusts of external origin, mainly from the countries of Iraq and Syria, so it is suggested that, for the accurate analysis of internal dust, factors such as drought and use change of the factors affecting the occurrence of dust are to be considered.