پديد آورندگان :
طبرستاني، شهربانو دانشگاه آزاد اسلامي، واحد علوم و تحقيقات، تهران، ايران , كمالي، غلامعلي دانشگاه آزاد اسلامي، واحد علوم و تحقيقات، تهران، ايران , وظيفه دوست، مجيد دانشگاه سراسري گيلان، گيلان، ايران , صحت كاشاني، ساويز پژوهشكده هواشناسي و علوم جو - هواشناسي، تهران، ايران
كليدواژه :
طوفان گرد و خاك همرفتي , الگوهاي هواشناسي , تصاوير ماهواره اي , عمق نوري هواويز
چكيده فارسي :
دراين مقاله رفتار طوفان همرفتي تهران مورخ 24 آوريل 2017، با ارزيابي الگوهاي ميان مقياس و خرد مقياس و فراسنج هاي هواشناسي مانند دما، رطوبت، فشار، نقطه شبنم، ميدان باد و ديد افقي شرح مي دهد. اين طوفان گرد و خاك به طور معمول همراه با تندي بالاي باد، افت دما، افزايش دماي نقطه شبنم، افزايش فشار و در نتيجه كاهش ديد رخ مي دهد. همچنين تحليل و رديابي رخداد مزبور توسط تصاوير ماهواره اي انجام گرفت. بررسي تصاوير گرد و خاك RGB سنجنده EUMETSAT ، در روز 24 آوريل مبين پيشروي گرد و خاك بر روي نواحي غربي، مركزي ايران و وقوع طوفان در استان تهران بوده و در ساعت UTC 12:00 ابر هاي سيروس مبين جبهه سرد كاملا به شمال غرب و مركز ايران پيشروي كرده است. همچنين سري زماني ميانگين روزانه ضخامت نوري هواويزها به منظور بررسي وقوع طوفان گرد و خاك و شدت آن مورد مطالعه قرار گرفت و مشخص شد بيشينه مقادير در روز 24 آوريل در ايران روي استان تهران مي باشد كه نمايانگر وجود مقادير بالايي از ذرات معلق در منطقه است. افزايش مقاديرPM10 به عنوان كميت هاي نمايش دهنده غلظت ذرات گرد و خاك مربوط به دو ايستگاه دانشگاه شريف و شهرري در ساعت 18:00 محلي، نيز وقوع طوفان گرد و خاك را تاييد مي كند.
چكيده لاتين :
On April 24, 2017, a dust storm occurred in Tehran, which lasted less than 2 hours, caused severe damages to properties. This paper describes the behavior of this storm by assessing the mesoscale and micro scale patterns, as well as meteorological parameters such as temperature, humidity, pressure, dew point, wind field, and visibility in the study area led to the occurrence of dust. In this study, these cold and strong downdrafts along with the cold front activity during the maximum temperature in Tehran province, on the surface and near surface layers, have been strengthened and intensified the wind velocity in the region, thereby causing the convective dust storm in Tehran province. This typically occurs at high wind speed, temperature drop, rise in dew point temperature and pressure, resulting in reduction of visibility. In synoptic analysis, it is noted that in the sea level pressure maps, a high-pressure system (1020 hPa) has eastward movement toward Russia and a low-pressure system affects northern areas of Iran, while the high-pressure center dominated over the south and southwest parts of Iran. The other high-pressure center (1020mb) has been formed in the eastern part of Syria. Also, a trough axis, along with a low-pressure cell affects the northern region of Iran and leads to a significant pressure gradient in northern areas (southern Alborz) and northwest of Iran. A significant increase in pressure is observed in the northern regions of Iran at 12:00UTC. At 850 hPa map, there is an instability in the northwest of Iran on 23April, the geopotential height contours crossed the isotherms strongly in the east of Syria, Iraq and west of Iran resulting in the solenoid formation on 24April at 00:00UTC. Consequently, baroclinic cell indicate the existence of an active cold front in the center part of Iran influencing Tehran province. A significant cloud cover formed in this region due to the cold front, especially in the northwestern and western parts of Iran. At 500 hPa map, on Monday 24April, at 00:00 UTC a deep trough leads to the large divergence formation in its eastern parts, especially in Iraq and Syria. A presence of the ridge over Iran provides conditions for preventing possible precipitation, especially in the Tehran province, while at 12:00 UTC, the divergence becomes stronger in the east of the trough over the Black Sea, Syria and Iraq. The dust storm was also analyzed and tracked by satellite imagery using dust product derived from MSG satellite images and the results revealed the movement of dust in west and central Iran and the signs of dust genesis in Tehran province as well as the movement of Cirrus clouds to north and northwest of Iran as a sign of cold front in this region. Cirrus clouds have been advanced to the northwest and center of Iran at 12:00 UTC. The PM10 and PM2.5 concentration related to I.R of Iran Department of Environment (DOE) air quality stations can be considered as a suitable measure of the concentration of natural mobilized dust particles. The increase of PM10 and PM2.5 values is in coincidence with visibility reduced as well.
