تحلیل همبست خشکسالی_گرد و غبار و بررسی ارتباط آن با تغییرات پوشش گیاهی در استان خوزستان

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی آبیاری و آبادانی، دانشکدگان کشاورزی و منابع طبیعی دانشگاه تهران، کرج، ایران.

چکیده

خشکسالی به عنوان یکی از پیچیده‌ترین پدیده‌های طبیعی هر ساله خسارت‌های زیادی به صورت مستقیم و غیرمستقیم به بخش‌های مختلف وارد می‌کند. هدف از مطالعه حاضر، پایش یکپارچۀ خشک‌سالی، گرد و غبار و پوشش گیاهی در پنج ایستگاه استان خوزستان با طول دورۀ آماری 30 ساله (2019-1990) می‌باشد. در این مطالعه از داده‌های ساعتی قدرت دید افقی، کدهای سازمان هواشناسی و همچنین داده‌های ایستگاه سینوپتیک در بازه زمانی روزانه برای به دست آوردن شاخص‌های خشک‌سالی (SPEI,SPI) و متغیر فراوانی طوفان‌های گرد و غبار (DU) در پنجره‌های زمانی 1، 3، 6 و 12 ماهه استفاده گردید. بعد از محاسبۀ شاخص‌های خشک-سالی، گرد و غبار و پوشش گیاهی، به ترکیب این شاخص‌ها با روش‌ تابع کاپولای تجربی پرداخته شد. ایستگاهی که بهترین همبستگی را بین سه شاخص اقلیمی گرد و غبار - خشک‌سالی - پوشش گیاهی به همراه داشت، به عنوان ایستگاه معرف در نظر گرفته شد و کوپل سه متغیره بین شاخص‌های مورد نظر در آن ایستگاه بررسی گردید. نتایج نشان داد که طبق شاخص SPI از سال 1999 تا 2003 و 2008 تا 2012 خشک‌سالی‌های شدیدی در سطح استان رخ داده است که تأثیرات منفی زیادی را بر خاک منطقه و همچنین شکل‌گیری کانون‌های مولد گرد و غبار در بازۀ زمانی مذکور داشته است. همچنین نتایج نشان داد که بالاترین همبستگی مربوط به ایستگاه بندر ماهشهر بین شاخص‌های NDVI و SPEI(PM12) به‌ترتیب با ضرایب همبستگی پیرسون و اسپیرمن 44/0 و 46/0 و بیشترین مقدار همبستگی منفی در ایستگاه مسجد سلیمان بین شاخص‌های NDVI و DU06 به ترتیب با ضرایب همبستگی پیرسون و اسپیرمن 37/0-  و 47/0- رخ داده است. نتایج به‌دست آمده در استان خوزستان تقریباً منطقی است زیرا با افزایش شاخص خشک‌سالی (کاهش میزان خشکی)، شاخص NDVI افزایش و با بیشتر شدن گرد و غبار مقدار NDVI کاهش یافت.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Correlation analysis of drought-dust and its relationship with vegetation changes in Khuzestan province

نویسندگان [English]

  • Haniyeh Mohammadi
  • Javad Bazrafshan
  • Abdolmajid Liaghat
Department of Irrigation and Reclamation Engineering, College of Agricultural and Natural Resources, University of Tehran, Karaj, Iran.
چکیده [English]

Drought, one of the most complex natural phenomena, causes significant direct and indirect damage to different sectors annually. The purpose of this study was to monitor drought, dust, and vegetation at five stations in the Khuzestan Province over a statistical period of 30 years (1990-2019). In this study, from the hourly data of horizontal visibility, the codes of the Meteorological Organization as well as the data of the synoptic station in the daily time frame were used to obtain the drought indices (SPEI and SPI) and the frequency variable of dust storms (DU) in time windows of 1, 3, 6, and 12 months. After calculating the indices of drought, dust and vegetation, they were combined with the empirical copula function method. The station that had the best correlation between the three climatic indices of dust-drought-vegetation was considered a representative station, and the three-variable coupling among the desired indices was investigated at that station. The results showed according to the SPI index, severe droughts occurred in the province from 1999 to 2003 and 2008 to 2012, which had a lot of negative effects on the soil of the region, as well as the formation of dust generating centers in the mentioned time period. Also, the results showed that the highest correlation was related to Bandar Mahshahr station between NDVI and SPEI (PM12) indices with Pearson and Spearman correlation coefficients of 0.44 and 0.46, respectively, and the highest negative correlation at Masjid Suleiman station between NDVI and DU06 occurred with Pearson and Spearman correlation coefficients of -0.37 and -0.47, respectively. The results obtained in Khuzestan Province are almost realistic as the drought index increased, the NDVI index increased, and as the dust increased, the NDVI value decreased.

کلیدواژه‌ها [English]

  • Dust
  • NDVI
  • Normalized Vegetation Index
  • Spearman correlation
  • three-variable couplet

Correlation analysis of drought-dust and its relationship with vegetation changes in Khuzestan province

 

EXTENDED ABSTRACT

Background

Changes in vegetation can have a significant effect on drought and dust in the western and southwestern regions of the country. Vegetation acts as an important factor in the balance of water and soil, the amount of transpiration evaporation, water absorption, reducing soil erosion, and stabilizing soil and dust particles. If vegetation cover decreases, transpiration evaporation decreases, which may lead to an increase in drought. On the other hand, drought can also have a significant effect on vegetation. Dust particles may also be deposited on the leaves and surfaces of plants, disturbing the performance of photosynthesis and transpiration evaporation of plants. Therefore, considering the importance and mutual influence of the three phenomena of drought, dust, and vegetation in the western regions of Iran, it is necessary to monitor and integrate the indicators of these three phenomena to determine the effects and mutual relations of the phenomena, which can be compared and discussed.

purpose

In this study, the integrated monitoring of drought, dust and vegetation in five stations of Khuzestan province (Ahvaz, Bandar Mahshahr, Bostan, Masjid Suleiman and Safi Abad) with a statistical period of 30 years (1990-2019) was done. For this purpose, from the hourly data of horizontal visibility, the codes of the Meteorological Organization, as well as the data of precipitation, minimum temperature, maximum temperature, sunny hours, relative humidity, and wind speed in the daily time window were used to obtain drought indices (SPEI and SPI). The frequency variables of dust storms (DU) were used in time windows of 1, 3, 6, and 12 months. In addition, to obtain the NDVI, Landsat satellite images were extracted monthly during the statistical period.

Methods

After calculating the indices of drought, dust, and vegetation, they were combined using the empirical copula function method. The station that had the best correlation between the three climatic indices of dust-drought-vegetation was considered the representative station, and the three-variable coupling between the desired indices was investigated at that station.

Results and Discussion

The results showed that according to the SPI index, severe droughts occurred in the province from 1999 to 2003 and 2008 to 2012, which had many negative effects on the soil of the region, as well as the formation of dust-generating centers in the mentioned time period. On the other hand, the SPEI-TH index, compared to other indices, can detect drought and accurately determine the sequence of periods. Also, the results showed that the highest correlation related to Bandar Mahshahr station between NDVI and SPEI (PM12) indices with Pearson and Spearman correlation coefficients of 0.44 and 0.46, respectively, and the highest negative correlation at Masjid Suleiman station between NDVI and DU06 occurred with Pearson and Spearman correlation coefficients of -0.37 and -0.47, respectively. The results obtained in Khuzestan Province are almost logical because with an increase in the drought index (incidence of drought or positive index), the NDVI index also increases, and as the dust increases, the NDVI value decreases.

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تحقیقات آب و خاک ایران
دوره 54، شماره 10
دی 1402
صفحه 1447-1465

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