nahid alipour

Dust storm is a phenomenon that occurs in arid and semi-arid regions due to high wind speed and turbulence on the surface of the soil without cover and prone to erosion. Dust changes the radiant budget of the earth's surface and changes the temperature of the earth's surface and atmosphere. Therefore, dust affects the energy exchange between the surface and the atmosphere as well as the dynamics of the atmosphere. Recognizing and studying the trend of dust storms and their relationship with climate change is one of the most important ways to reduce the damage caused by this phenomenon. This study amies to evaluate the effect of dust storms on radiation indices and heat flux according to the combination of satellite remote sensing information and re-analysis data in Hirmand basin.

In this research ERA5 re-analysis and Terra satellite data used for the August 23-26, 2010 event in Hirmand. Products and satellite data used including true color images and AOD and re-analysis data including Surface latent heat flux (SLHF), Surface Sensible Heat Flux (SSHF), Surface net Solar Radiation (SSR), Surface net Thermal Radiation (STR) and Balance Radiation (Rn). Dust particles were routed using the HYSPLIT model and wind speed in the study area was also assessed using the analysis data. Also, for validation of satellite data and re-analysis, visibility and air temperature data, at height of 2 meters, at Zabol Meteorological Station, closest station to the study area, were analyzed.

According to the HYSPLIT model output, most of the dust particles were collected from the deserts of Turkmenistan and then the dry areas around Lake Hamun and parts of northern Pakistan. AOD values showed that from August 21, the value of this index gradually increased so that on the 25th day, the maximum AOD value reached 1.25. Examination of the values of radiation and heat flux indices showed a significant decrease in SSHF, SSR, STR and Rn indices and their values reached the lowest value on the 26th day and the SLHF index with a slight difference on the 25th day reached its lowest value of 58 w/m2. Correlation study showed that SSR and Rn indices with -0.370 and -0.359 respectively had the highest and SLHF index with -0.153 showed the lowest correlation with AOD index.

The results of this study showed that the western parts of Hirmand Basin, Lavar or North wind has emitted dust particles into atmosphere, and the region and rotational currents has caused the distribution of these particles in the study area. The results of satellite data and their re-analysis and matching with real images showed that the study event increased the optical depth of dust particles, which resulted in tangible and surface heat fluxes, solar and thermal radiation, as well as balance. Radiation was greatly reduced. Evaluation of horizontal visibility and air temperature data at a height of 2 meters at Zabol station also confirmed the results of satellite images and re-analysis data.

Dust phenomenon is one the problem that is developed due to human interference and unreasonable utilities from natural resources and their destruction. In this review, the dust phenomenon frequency was done using selected synoptic stations statistical in Alborz and Qazvin provinces during 2000 to 2014 that annual frequency was evaluated by extraction of dust codes from meteorological data statistically. In order to study of velocity and direction of region winds, wind rose and storm rose of Karaj and Qazvin stations were drew and prevalent wind direction was determined that it showed prevalent wind is northwest and southeast at Karaj and Qazvin stations respectively. Study of the effect of drought on dust phenomenon event was done using SPI, PNI, ZSI indicator for annual scale and was evaluated via SPSS software. The drought result show that 2013 was the driest year at Karaj station and the SPI, PNI and ZSI values were obtained -1.64, 58 and -1.39 respectively. Also 2008 was the driest year at Qazvin station and SPI, PNI and ZSI values were calculated -2.34, 50 and -1.99 respectively. With studying of annual dust frequency with regard to 06 and 07 codes detected that totally 169 days was reported as day with dust at Karaj station that 2012 and 2014 had the most event frequency. Furthermore, totally 115 days with dust accrued at Qazvin station that 2011 with 23 days had the most event frequency.

Statistical investigation of dust phenomenon in Alborz and Qazvin provinces 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 & 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. 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. 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.

Dust storm is a phenomenon that mainly occurs in arid and semiarid regions in the result of high speed of wind and its turbulence on soil surface without coverage and erosion competent and cause to view amount reduction to less than 1 kilometer. In this study, dust and precipitation data in synoptic station selected in Alborz and Qazvin provinces was used during 2000 to 2014. After 06 and 07 codes extraction from meteorology data, days with dust were detected and monthly and yearly frequency of dust were analyzed statistically. evaluation of drought effect on the dust phenomena occurrence was performed using the SPI method for annual and monthly scales at 3, 9 and 18 months intervals. The drought results showed a severe drought at the Karaj station in 2013 and an extreme drought at the Qazvin Station in 2008. The result of investigation of annual dust showed that Karaj and Qazvin stations with regard to 06 and 07 codes had the highest dust phenomenon. Monthly evaluation also showed that the most frequent events occurred at the stations of Karaj and Qazvin in the months of May and June. By examining the relationship between drought and the frequency of days with dust, it was also found that there was no significant correlation between these two phenomena at the Karaj station on an annual and monthly scale, but at Qazvin Station between days with dust and SPI values in the 18-month interval, there was a weak correlation in 10% level, but there was no significant relationship between other time scales.

Drought is an insidious environmental phenomenon. This phenomenon causes water shortage for some activities, communities or environment. Drought should be compared with average climate and hydrological Conditions for Long period of time. Hydrological drought is detected by reduced water storage in lakes, underground water levels drawdown and reduced river flow and often will affect a large area. The most common definition of a hydrological drought is to define a threshold limit, such that if the river is less than that, a hydrologic drought is considered. In this study, the fixed threshold limit of Q70 was used in Karaj drainage Basin. Results showed that Q90 of year 1998 was the driest year. The results show that 1377 year was one of the driest years in this area and in Karaj station 284 days and for Gachsar station 255 days were dry. Also, the results show a total lack of water in Gachsar station Q70 threshold equal to 68/11 million cubic meters, Kalavan stations equivalent to 75.2 million cubic meters and for Karaj station equal to 44/42 million cubic. The general extreme value (GEV) best fit the parameters of the drought. The results can be used in water resources management and planning necessary to prevent or mitigate the effects of drought in the area.