بررسی همدیدی روزهای بسیار آلوده درشهرمشهد مورد مطالعه: 13و14نوامبر2007

به منظور تحلیل همدیدی روزهای بسیار آلوده در13و14 نوامبر 2007 از یک روش تحلیل همدیدی ترکیبی استفاده شد. در پژوهش حاضر، چهار دسته داده، شامل داده های آلودگی ثبت شده در ایستگاه های سنجش آلودگی هوا، داده های رقومی جوی، داده های ایستگاه جو بالا و خروجی های مدلhysplit مورد استفاده قرار گرفت. داده های آلودگی هوا از سازمان حفاظت محیط زیست خراسان رضوی، داده های جوی از مرکز ملی پیش بینی محیطی/مرکز ملی پژوهش جو(ncep/ncar) و داده های جو بالای ایستگاه مشهد از دانشگاه وایومینگ تهیه شد. ردیابی ذرات معلق نیز با بهره گیری از نسخه آنلاین مدل لاگرانژینیhysplit و با استفاده از روش ردیابی پسگرد به انجام رسید. نتایج تحلیل همدیدی بیانگر آن است که روزهای بسیار آلوده 13و14نوامبر2007در شهر مشهد در قالب الگوی پرفشار مهاجرقابل طبقه بندی است .در الگوی پرفشار مهاجر،عبور امواج غربی از روی منطقه، استقرار پشته ای قوی در محدوده رشته کوه های اورال و دریای خزر را در پی دارد که با یک اریب شرق سو شکل گیری مرکز گردش واچرخندی را در حدفاصل دریای خزر تا بخش های شمالی خراسان در ترازهای زیرین موجب می گردد.دراین الگو شاهد شکل گیری همزمان چند لایه کم ضخامت وارونگی در زیر تراز 400 هکتوپاسکال هستیم.

Synoptic Analysis of the Severe Polluted Days in the City of Mashhad

For a synoptic analysis of high polluted days in 13 and 14 November 2007, a combinatorial synoptic analysis was used. From methodology prospect, the present study has utilized the circular environment synoptic approach and with respect to the restrictions on very highpolluted days in Mashhad city, the subjective synoptic analysis used for data processing and analyzing the prevailing atmospheric conditions.In the present research, four sets of the data, including the pollution data recorded at the stations monitoring air pollution, digital atmospheric data, data of upper air stations and the outputs of HYSPLIT model were utilized. The data on air pollution obtained from the Department of Environment Protection of Khorasan Razavi were related to Wahdat station located in the center of Mashhad city. The pollutants include CO, NO2, SO2, ozone, and particulate matter (PM10( prepared and processed on a daily scale for a 7year statistical period (20052012). When studying the quality of air pollution over Mashhad city, it is necessary to indicate that Mashhad city had only one station monitoring air pollution (Wahdat station) until 2010 and unfortunately, out of 10 present stations for monitoring the air pollution, only Wahdat station was involved a suitable statistical period duration to be studied. Accordingly, the present study has been conducted only by using the pollution data recorded in Wahdat station and utilizing the data of other stations ignored due to the shortness of statistical period duration. The reanalyzed data of the National Centers for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) with a horizontal separation 2.5 times; 2.5 were used in order to study the atmospheric conditions. The atmospheric conditions include the sea level pressure, geopotential height, vertical velocity, and orbit wind (u) meridian wind (v) components on different atmospheric levels from the past 48 hours and in a 6hour interval. In addition, upper air data about Mashhad station (Mashhad airport) were used on a similar period. Upper air data have been obtained from the website of Wyoming university (http://weather.uwyo.edu/upperair/sounding.html) on under study days, including air temperature, dew point, direction, wind intensity and the atmospheric stability and instability conditions (based on SkewT Curves ndash; logP). These data are only available on Zero Greenwich hour. The outputs of the HYSPLIT model were also used as complementary data for tracing particulate matter in days 10 15 in November. In this study, the HYSPLIT model, version 4.9 was used. In the present research, the role of regional atmospheric circulation and pressure patterns were investigated on a synoptic scale in very highpolluted days in November 2007 in Mashhad metropolitan. For this purpose, the mechanism dominated on occurring a very highpolluted period in this city was analyzed using a combinatorial method based on synoptic and thermodynamic analyses as well as tracing particulate matter. The results of studies involve the following findings: the days 13 and 14 November 2007 (22 and 23 Aban, 1386) show the highest concentration rates among the polluted days in Mashhad city. The findings of the research show that the synoptic pattern dominated the very high polluted period (13 and 14 November 2007) is a migrant highpressure pattern. Accordingly, it may be concluded that the incidence of serious pollutions in Mashhad is initially the result of interacting local conditions with air circulation on a regional scale and then the other local factors. In the other words, Mashhad city would experience very highpolluted days only when regional atmospheric circulation provides suitable conditions to increase the concentration of pollutants. What is obvious is that in the winter season the serious pollutions occurred in Mashhad city are mainly as the results of prevailing extratropical systems (migrant anticyclone). Studying subjective synoptic analysis, tracing the backtracking of particulate matter and the atmospheric thermodynamic conditions ( combinatorial synoptic analysis) have provided a deeper and more accurate understanding of the conditions prevailing in the occurrence of serious pollutions in the northeast of Iran. Studying the output of the HYSPLIT model indicates that the migrant stack system of western wave together with the subtropical stack would control the air circulation pattern on the northeast of Iran in 13 and 14 November 2007. Tracing the particulates shows an anticyclone system on the zone. Also, studying SKEWT Curves related to the migrant highpressure pattern revealed a different structure, so that the day 12 November 2007 faced with a radiation inversion along with an increased temperature, but on day 13 November 2007 an inversion from the sort of subsidence between the interval of level 850 to 700 hpa was appeared and also reached to higher than 700 hpa.