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Abstract:  
Introduction
The phenomenon of dust in recent years in the cold season has become a serious problem in Khuzestan province. The purpose of this study was to investigate and analyze the synoptic pattern of sweeping dusts in Khuzestan province during the cold season.
 
Materials and methods
 
In order to study and analyze the synoptic pattern of dust in Khuzestan province in the cold period of the year, two databases have been used. Atmospheric Database: After extracting the dust codes, the all-day dust day was said to be the day when at least 50 percent of the spatial coverage lasted for two days. After extracting the all-round dust days, the corresponding pressure data have been extracted with these days. This part of the data includes ground pressure data, geopolitical altitude, moisture depletion and atmospheric precipitation for levels of 100 to 500 hpa. (NCEP / NCAR) received. According to the research topic and in order to fully display the effective systems in creating dust, the study range of atmospheric systems is determined from -10 degrees west longitude to 100 degrees east longitude and 10 to 70 degrees north latitude. Has been. In the present study, an attempt has been made to identify and analyze the effective patterns in creating dust in Khuzestan province by using an environmental approach. In the next step, with the help of cluster analysis on the corresponding pressure data with these days, the pattern of dust days has been identified. After extracting the corresponding pressure data these days, cluster analysis has been used to identify the dust patterns of Khuzestan province. In the next step, with the aim of classifying the pressure data on the ground and identifying the representative days, cluster analysis was performed on these data. Cluster analysis is a method in which variables are classified into specific groups based on their characteristics In order to select the representative days of the groups obtained from the classification of data related to dust, the Lund correlation method has been used The amount of correlation coefficient in such cases typically varies between 0.5 and 0.7. Representative days were extracted based on the threshold of 0.5. Thus, the day that has a correlation coefficient of 0.5 with more days was selected as the representative day.
 
Result
By performing cluster analysis on pressure data along with days with Khuzestan comprehensive dust in the cold period of the year, 4 patterns have been identified.
These patterns include 1) low pressure of the Caspian Sea - high pressure in Siberia, high pressure in Europe. 2) European Integral Pressure, Mediterranean - Sudan Pressure, North Caspian Pressure. 3) The low pressure of the Arabian Sea and the high pressure of North Africa. 4) Siberian high pressure - Sudan low pressure and low Mediterranean pressure; among them, the first model (low pressure of the Caspian Sea - high pressure in Siberia, high pressure in Europe) has the highest frequency. Then, after identifying the days of dust and performing cluster analysis on.
 
Discussion and Conclusion
Above 20 degrees, Iraq, northern Saudi Arabia and eastern Syria are the main causes of dust formation in the region. The situation, along with the westerly winds in parts of the Middle East that are prone to dust supply and production, will eventually exacerbate desertification in North Africa. In this regard, environmental conditions along with increasing temperature, low humidity and wind speed and lack of complete adhesion of soil particles along with atmospheric factors that cause the spread of instability in these areas are quite effective in creating this phenomenon; Sudan's low-temperature thermal tabs are stretched to higher ranges and their nature changes dynamically when the Mediterranean or Red Sea lands in the deserts of Saudi Arabia and Africa, along with a deep pressure gust formed in the eastern Mediterranean. In the middle layer, the troposphere is the main producer of dust in the south-west of the country and Khuzestan province.Therefore, when a deep landing in the eastern Mediterranean is created, the flows of the east side coincide with the North African currents and eventually merge with the high divergence in the southwestern part of the country, provided environmental conditions are provided. The instability at ground level due to the low sea-level pressures on the great deserts of the Middle East will lead to the phenomenon of dust in Khuzestan province.
     
Type of Study: Research | Subject: Climatology
Received: 2020/07/7 | Accepted: 2020/11/22