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پژوهش های اقلیم شناسی، جلد ۱۴۰۴، شماره ۶۱، صفحات ۱۱۱-۱۲۵
عنوان فارسی ارزیابی تغییرات روزانه غلظت ذرات ریز معلق(PM۲.۵) در فازهای نوسان مادن- جولیان(MJO)
چکیده فارسی مقاله مواردی از رخداد همزمان یا با فاصله چند روزه پدیده افزایش غلظت ذرات ریز معلق با قطر آیرودینامیکی 5/2 میکرومتر (PM2.5) در ایستگاه های پایش گرد و غبار، پایه این پژوهش بوده است. بررسی اولیه داده های غلظت PM2.5 در این ایستگاه ها نشان داد این افزایش در تاریخ های مشابه یا نزدیک به هم رخ داده است. ارزیابی تغییرات غلظت این ذرات در برابر دو متغیر متناسب با مقیاس زمانی این پدیده (روزانه) صورت گرفت. برای این کار داده های روزانه سری زمانی PM2.5 و بیشینه سرعت باد روزانه (DMWS) با فازهای هشتگانه پدیده نوسان مادن- جولیان (MJO) برای تمام روزهای فصل زمستان( دسامبر، ژانویه و فوریه) در دوره سال های 2013 تا 2020 مطابقت داده شد. سپس پیوند میان روزهای آلودگی هوا به این ذرات (PM2.5 > 35 μgm-3) و بیشینه سرعت باد روزانه سه ایستگاه هواشناسی همدیدی اصفهان، مشهد و یزد با فازهای MJO بررسی گردید. ارزیابی‌ داده‌های این سه ایستگاه بر پایه روش‌های آماری متداول از جمله رگرسیون خطی، آزمون‌های کای اسکوئر(𝜒2) ، کولموگروف – اسمیرنوف (K-S) و آزمون تک نمونه ای student’s t استوار بوده است. همبستگی PM2.5 و سرعت باد نشان داد که با افزایش سرعت باد، آلودگی هوا به PM2.5 در هر سه ایستگاه کاهش یافته و روند کاهشی در اصفهان بیشترین و در یزد کمترین است. همچنین یافته ها نشان داد که فراوانی روزهای آلوده در سرعتهای بالای وزش باد (چارک1) به گونه ای معنی‌دار کمتر از فراوانی آنها در سرعت‌های پایین باد (چارک4) است. در فاز 5 نوسان مادن جولیان سرعت باد کمترین اندازه و غلظت‌های بالای این ذرات بیشترین مقدار را نشان داد. همچنین فاز 5 MJO بیشترین فراوانی روزهای بالاتر از میانگین فصلی (PM2.5 > 20 μgm-3) را داشت. بیشترین فراوانی روزهای با هوای پاک (PM2.5 < 35 μgm-3) نیز در فاز 7 نوسان مادن- جولیان دیده شد.
کلیدواژه‌های فارسی مقاله آلودگی هوا،ایستگاه پایش گرد و غبار،بیشینه سرعت باد روزانه،ذرات ریز معلق،نوسان مادن – جولیان،
عنوان انگلیسی Evaluation of daily changes in the concentration of particulate matters (PM2.5) in the phases of the Madden-Julian Oscillation (MJO)
چکیده انگلیسی مقاله ABSTRACT

The basis of this research was the observation of cases occurrences at a same time or with a short time delay of an increase in the concentration of PM2.5 in several meteorological stations. For this purpose, the relationship between air pollution for winter days with the Daily Maximum Wind Speed of meteorological stations in Isfahan, Mashhad and Yazd and the phases of MJO was assessed. The phase number of the MJO for all days of the study period (2013-2020) used to match the PM2.5 and wind speed. The data evaluation was based on the statistical methods of linear regression and chi-square (𝜒2), Kolmogorov-Smirnov (K-S) and single-sample student's t tests. The correlation between PM2.5 and wind speed showed that with the increase in wind speed, air pollution with PM2.5 decreased in all three stations and the decreasing trend was the highest in Isfahan and the lowest in Yazd. The findings showed that the frequency of polluted days (PM2.5 > 35 μgm-3) in high wind speeds (quartile 1) is significantly lower than their frequency in low wind speeds (quartile 4). In MJO phase 5, wind speed was the lowest and high concentrations (PM2.5 > 35 μgm-3 & > 20 μgm-3) showed the highest value. MJO phase 5 had the highest frequency of days above the seasonal average (PM2.5 > 20 μgm-3). The highest frequency of days with clean air was also seen in phase 7.



Keywords: Air Pollution, Dust measurement station, Particulate Matters, Phase of MJO, Daily Maximum wind speed







Extended Summary

Introduction

Fine particles with an aerodynamic diameter of less than 2.5 micrometers (PM2.5) play one of the greatest roles in air pollution. Also, these particles affect meteorological characteristics such as the amount of radiation, the earth's surface temperature and the horizontal visibility. The concentration of these particles in the air depends on the geographical location, land use and land cover, weather conditions and different periods of time. climate characteristics are one of the most fundamental controllers of the concentration and distribution of pollutants. Hence, phenomena such as El-Nino Southern Oscillation (ENSO) and Madden Julian Oscillation (MJO) that transform the world's climate on a continental to local scale have a great role in identifying their impact on air pollution. In this study we assessed the relationships between wintertime concentrations of PM2.5 and two meteorological-climatological components comprising surface wind speed and the Madden Julian Oscillation (MJO) in five Iranian meteorological stations.





Data and Methods

Data:

We used the official webpage of the Iranian meteorological Organization (IRIMO) to extract the hourly data of PM2.5 in five Iran’s synoptic meteorological stations (Esfahan, Bam, Mashhad, Yasuj and Yazd) during the wintertime (January-March) of the period 2013 to 2020. The data are available at https://Pollution1.irimo.ir. Since the magnitudes of these concentrations in Bam and Yasuj were predominantly less than 35 µg/m3, we decided to exclude the data of these two stations from further analyses. Also, the daily values of maximum wind speeds (m/s) in the afore mentioned meteorological stations were obtained for the wintertime of 2013-2020. The daily time series of the MJO characteristics and particularly the phase number were extracted from the relevant webpage for all days of the study period to match the PM2.5 and wind velocity data. These data are available in: http://cawcr.gov.au/staff/mwheeler/maproom/RMM for the period 2013 to 2020.



Methods:

In each meteorological station, the magnitudes of three variables comprising PM2.5, wind speed and the MJO phase numbers were assigned to each day of the study period. Moreover, wind speed and MJO characteristics were assessed for those days of the study period when the PM2.5 concentrations were greater than either 35 µg/m3 or 20 µg/m3. After collecting the mentioned statistics in each station, the regression analysis was conducted to evaluate the wind speed-PM2.5 correlations. We then constructed the a few (2×2) contingency tables and conducting the relevant Chi-square (𝜒2) statistical tests to assess if the frequency of the polluted and clean days was statistically related to the frequencies of the days with very high (Q1) or very low (Q4) wind speed. We examined both 35 µg/m3 and 20 µg/m3 thresholds to split clean from polluted days. Notably, 20 µg/m3 was almost the mean value of PM2.5 concentration within the study period. Also, the study compared the frequency of the polluted and clean days within the MJO eight phases. In other words, we investigated if the PM2.5 concentrations are statistically different between the MJO phases.



Discussion of results

The negative correlations between wind speed and the PM2.5 concentrations showed that the high (low) values of these concentrations are associated with low (high) wind speeds. These negative associations were approved by the outcomes of the employed Chi-square test where the frequency of those polluted days coinciding with the high-speed wind (Q1) was significantly less than that during the low-speed wind (Q4). Generally, the frequency of clean days was more (less) during those days that are specified as very high (low) wind speed. Our results showed that the frequency of the polluted (clean) days was the highest during the MJO-phase 5 (7). After phase 5, the highest frequency of the polluted days was related to the MJO-phase 6. Also, we examined the ratio of the polluted to the clean days during every MJO phase. Regardless of using 35 µg/m3 or 20 µg/m3 threshold or the studied stations, the ratio was highest during phase 5. Also, the average concentration of PM2.5 in phase 5 of MJO showed a significant difference with two thresholds (20 & 35 µg/m3) of these particles.



Conclusions

The correlation and Chi-square tests proved that high (low) wind speed reduces (increases) the frequency of the polluted days. During the MJO phase 5, when wind speed was consistently lower than the other MJO phases, air contamination by PM2.5 and the ratio of the polluted to clean days were higher than the other phases. If 20 µg/m3 is considered as the threshold of the clean and polluted days, phases 3 and 8 could be specified as the cleanest MJO phases.
کلیدواژه‌های انگلیسی مقاله آلودگی هوا,ایستگاه پایش گرد و غبار,بیشینه سرعت باد روزانه,ذرات ریز معلق,نوسان مادن – جولیان
نویسندگان مقاله محمد جعفر ناظم السادات |
استاد، بخش مهندسی آب، مرکز پژوهش‌های علوم جوی و اقیانوسی، دانشکده کشاورزی، دانشگاه شیراز

علیرضا دشتی رحمت آبادی |
دانشجوی دکترا، بخش مهندسی آب، مرکز پژوهش‌های علوم جوی و اقیانوسی، دانشکده کشاورزی، دانشگاه شیراز

نشانی اینترنتی https://clima.irimo.ir/article_222974_4b7601299a595b4bd83e3aeb104eb8a9.pdf
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