Abstract:
در این پژوهش به تحلیل آماری رخداد طوفان های گرد و غبار با استفاده از داده های ایستگاه هواشناسی همدیدی خراسان رضوی پرداخته شد. بر اساس دستورالعمل سازمان جهانی هواشناسی، هرگاه در ایستگاهی سرعت باد از 30 نات بیشتر شود و دید افقی به علت پدیدة گرد و غبار به کمتر از یک کیلومتر برسد، طوفان گرد و غبار گزارش میشود. کدهای 30 تا 35 مربوط به طوفان گرد و غبار یا شن معرفی میشود. در این تحقیق، نخست فراوانی رخداد طوفانهای گرد و غبار در ایستگاههای همدیدی خراسان رضوی طی سالهای 1331-1398 بررسی شد. سپس، به صورت موردی به بررسی رخداد طوفان گرد و غبار در مشهد به علت ایجاد وضعیت بحرانی در این کلانشهر در تاریخ 25/7/1396 برای بررسی مسیر ورودی این طوفانها پرداخته شد. بررسی تصاویر ماهوارة مودیس و تحلیلی الگوی گرد و غبار و همچنین ردیابی بستههای هوا حامل ذرات گرد و غبار با استفاده از مدل HYSPLIT با روش پسگرد و پیشگرد در ایستگاه مشهد بهعنوان یکی از مهمترین ایستگاه های هواشناسی شمال شرق کشور انجام شد. نتایج نشان داد بیشترین فراوانی طوفانهای گرد و غبار در سطح استان مرتبط با سبزوار با 136 طوفان ملایم و 79 طوفان شدید و شهرهای سرخس و گناباد در رتبه های بعدی بوده اند. با ردیابی و آشکارسازی پدیدة طوفان گرد و غبار به صورت موردی مشاهده شد که این پدیده نخست بر روی ترکمنستان شکل می گیرد و با نفوذ به مرزهای شرقی کشور شهر مشهد را تحت تأثیر قرار می دهد.
Climate analysis and study of dust storms in Khorasan RazaviIntroductionDust and air pollution from dust are of important social and everyday issues in society. According to the Earth Observatory website dust storms are considered natural hazards, which affect ecosystems for short time intervals ranging from a few hours to a few days. Dust outbreaks have a significant impact on climate, human health and ecosystems, and numerous studies have been conducted worldwide with different instrumentation and techniques to investigate of such events. In addition to human health problems, these phenomena impose much damages to industrial and agricultural installation, population centers and communication ways. The recognition of source regions, creation and expansion style of dust storms and their relation with atmospheric circulation patterns are fundamental factors in reduction of their damages this has affected major decision-makings and policies. Dust particles enter the atmosphere under the influence of various factors such as weather conditions, ground surface characteristics such as topography, surface moisture, roughness and rough length and vegetation and soil characteristics (texture, density and composition) and land use (agriculture). Dust particles enter the atmosphere from the soil surface, rocks, volcanic lavas or environmental pollution and can lead to reduced evaporation, lowering the surface temperature and affect the precipitation process. Dust storms are one of the destructive climatic phenomena which are affected by various climatic elements such as pressure, precipitation, wind, temperature and evaporation. Dust storms are more common in arid and semi-arid regions and are far more important. Khorasan Razavi province has an arid and semi-arid climate with several dust storms occurring on its surface every year.Materials and methodsStatistical study of dust storms and tracking and revealing the path of these storms is important. In this study, statistical analysis of dust storms was performed using data from Khorasan Razavi Synoptic Meteorological Station. According to the World Meteorological Organization (WMO) guidelines, when wind speeds exceed 30 knots per station and horizontal visibility is less than one kilometer due to the dust phenomenon, a dust storm is reported and, the WW = 30-35 codes related to dust or sand storms are introduced, the occurrence of these codes in Khorasan Razavi synoptic stations was investigated. In the next step, the source of the dust storm event was investigated as a case study on 10/17/2017 using the image of MODIS satellite in Mashhad. Monitoring of dust source region, transport pathways and plume characteristics is only possible from satellites because ground-based measurements are very limited in space and time. Therefore, it is important to identify, also for prognostic purposes, the atmospheric circulation patterns facilitating the transport of dust particles from their source regions over distances of thousands of kilometers downwind. Compared to ground-based measurements, satellite observations offer a more efficient way of determining key characteristics of aerosols at temporal and spatial scales that are needed to study and monitor aerosol impacts upon the climate system. The Modis sensor was used to detect the path of the phenomenon and to examine satellite images. Compared to other sensors, MODIS measures the entire earth's surface in 36 bands, covering from the visible band (0.415 micrometers) to the thermal infrared (14235 micrometers). The Modis sensor is a high radiometric resolution (12-bit) device which is carried by two American satellites, Terra and Aqua. The crossing time of the two Terra and Aqua satellites along the equator is at 10:30 and 13:30 local time. In this study, images of the MODIS visible True color band with a resolution of one kilometer on the date under study in the area were received from NASA. Aerosol Optical Depth (AOD) is one of the most important parameters in the study of dust. The Aerosol Optical Depth actually refers to the distribution of dust aerosols in the atmosphere. This wavelength-dependent quantity is defined as the decrease in light per unit length on a given path Aerosol Optical Depth (AOD) is the degree to which aerosol particles prevent the transmission of light. It is defined as the integrated extinction coefficient over a vertical column of unit cross-section. It is an indirect measurement of the size and number of concentrations of aerosol particles present in a given column of air. The spectral dependency of AOD contains information about the dominance of fine and coarse mode particles, the aerosol source regions, the modeling of aerosol radiative effects, the air quality (through monitoring of particulate matter), and the correction for aerosol effects in satellite remote sensing of the Earth’s surface. Aerosol Optical Depth (AOD) maps were obtained with a spatial resolution of 0.1 by 0.1 degree and were received at three-hour time intervals from the Barcelona Forecast Center for the study. After the dust storm was detected and the source areas were identified, the tracing of the dust particles to Mashhad was determined using the HYSPLIT mode. The HYSPLIT model, which is a dual model, was used to calculate the dust trajectory, dispersion, and simulate it. HYSPLIT is a complete model for computing trajectories, complex dispersion, and deposition simulations using either puff or particle approaches. It is plausible to detect transport pathways through monitoring the dust source region in HYSPLIT. Developed by National Oceanic and Atmospheric Administration (NOAA), it is a Lagrangian model. This model is widely used for air parcel dispersion, transportation, and deposition simulation.Results and discussionThe results showed that the highest amount of dust storms is associated with Sabzevar with 136 mild storms and 79 severe storms and Sarakhs and Gonabad were in the next ranks. The dust phenomenon was observed case-by-case by detection and tracking that, this phenomenon has been formed in Turkmenistan in the early hours and affected Mashhad by penetrating the eastern borders of the country. According to satellite imagery, the origin of the dust storm in history has been in parts of Turkmenistan northeast of Mashhad. The output of HYSPILT maps shows good overlap with satellite imagery. This path has also been overlapped in AOD and Trajectory_Wind survey. In general, it can be stated that initially the primary dust cores were formed in the Turkmen desert and the density of dust increases as it moves west, and it has penetrated to the west and on the eastern borders of Iran and then to the city of Mashhad.ConclusionDust storms are observed and recorded at meteorological stations as a weather phenomenon that is categorized according to the degree of visibility deterioration. In this study, the days with dust storm (observation code 30 to 35, present weather), the synoptic analysis of wind speed, horizontal visibility and weather conditions have been adopted. The results showed that the highest amount of dust storms is associated with Sabzevar with 79 severe storms and Sarakhs and Gonabad were in the next ranks. Studieswith the various methods have shown that initially the primary dust cores were formed in the Turkmen desert and the density of dust increases as it moves west, and it has penetrated to the west and on the eastern borders of Iran and then to the city of Mashhad.Keywords: Dust storm, Khorasan Razavi, MODIS, HYSPLIT.
Machine summary:
بررسي تصاوير ماهوارة موديس و تحليلي الگوي گرد و غبار و همچنين رديابي بسته هاي هوا حامل ذرات گرد و غبار با استفاده از مدل HYSPLIT با روش پسگرد و پيشگرد در ايستگاه مشهد به عنوان يکي از مهم ترين ايستگاه هاي هواشناسي شمال شرق کشور انجام شد.
بررسي و مطالعۀ طوفان هاي گرد و غبار امري ضروري است و استفادة هم زمان از داده هاي ماهواره اي همراه مدل کاربردي و دوگانۀ HYSPLIT به همراه تحليل و بررسي آماري ميتواند بسيار مفيد و کاربردي براي منطقۀ مورد مطالعه باشد.
موقعيت جغرافيايي و تاريخ تأسيس ايستگاه هاي همديدي استان خراسان رضوي 1 بردسکن 1999 1378 985 57/97 35/27 ٢ درگز 2007 1386 514 59/07 37/47 ٤ گلمکان 1984 1363 1176 59/28 36/48 ٥ گناباد 1986 1365 1056 58/68 34/35 7 کاشمر 1985 1364 1109/7 58/47 35/27 9 مشهد 1949 1328 999/2 59/62 36/23 ١٠ نيشابور 1990 1369 1213 58/8 36/27 ١١ قوچان 1983 1362 1287 58/45 37/12 ١٢ سبزوار 1954 1333 972 57/65 36/2 ١٣ سرخس 1984 1363 278 61/13 36/53 ١٤ تربت حيدريه 1958 1337 1451 59/22 35/27 ١٥ تربت جام 1992 1371 950/4 60/55 35/28 بر اساس دستورالعمل سازمان جهاني هواشناسي (WMO)١، هرگاه در ايستگاهي سرعت باد از ٣٠ نات (١٥ متر بر ثانيه ) بيشتر شود و ديد افقي به علت پديدة گرد و غبار به کمتر از يک کيلومتر برسد، طوفان گرد و غبار گزارش ميشود (٣٠٦.
Simulation of Dust aerosol and its regional feedbacks over East Asia using a regional climate model, Atmospheric Chemistry and Physics Discussions, 8: 4625-4667.