مقایسۀ تغییرات دمای آب دریای عمان و خلیج فارس با دریای خزر با استفاده از تصاویر ماهواره ای (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
دمای سطح یا رویه آب در آب های آزاد و دریاچه ها به عنوان یکی از شاخص های سنجش ویژگی های اقیانوس شناسی و هواشناسی شناخته می شود. در این پژوهش، برای تحلیل تغییرات زمانی و مکانی دمای سطح آب دریای عمان، خلیج فارس و خزر با استفاده از داده های (25/0 درجه) سنجنده AVHRR طی بازه زمانی 1989-2019 استفاده شد. میانگین دمای ماهانه، فصلی و سالانه از داده های روزانه در نرم افزار ArcGIS 10.8 تهیه شد. سپس روند تغییرات دمایی آب در خلیج فارس و دریای عمان نسبت به دریای خزر بررسی شد. نتایج تحلیل داده های دمای سطح آب نشان دهنده آن است که در خلیج فارس و دریای عمان کاهش دما در قسمت شمالی خلیج فارس در فصل بهار و در عین حال، در فصل تابستان، در قسمت مرکزی خزر اتفاق افتاده است. در فصول پاییز و زمستان، کاهش دما متأثر از عرض جغرافیایی است؛ در حالی که در بخش های جنوبی دریای خزر به خصوص جنوب شرقی گرم ترین پهنه ها بوده است و خزر میانی نیز دمای کمتری نسبت به بقیه مناطق دارد. در فصل بهار، کاهش دما در خزر میانی اتفاق افتاد و به سمت عرض های بالا و پایین افزایش دما مشاهده شد؛ در حالی که در فصل پاییز کاهش دمای سطح آب در خلیج فارس و در زمستان در دریای عمان مشاهده شد. روندهای ماهیانه دما برای خلیج فارس و دریای عمان برای 12 ماه افزایشی است. در دریای خزر، روند تغییرات دما در ماه های ژانویه و دسامبر کاهشی و بقیه ماه ها افزایشی بود.Investigation of Sea Surface Temperature Changes in the Oman Sea and the Persian Gulf Using Satellite Images and Its Comparison with the Caspian Sea Trend
Water surface temperature in open seas and lakes is known as one of the indicators for measuring oceanographic and meteorological characteristics. In the present study, the data from the AVHRR sensor (1989-2019) have been used to analyze the temporal and spatial changes in water surface temperature of the Persian Gulf and Oman Sea. Average (monthly), seasonal, and annual temperatures were obtained from daily data in ArcGIS 10.8 software. Then, the trend of water temperature changes in the Persian Gulf and the Oman Sea compared to the Caspian Sea was investigated. The results of the water surface temperature data analysis showed that the water temperature in the Persian Gulf and the Oman Sea decreased in the northern part of the Persian Gulf in the spring, but in the summer, the temperature decreased in the central part of the Caspian Sea. In autumn and winter, the temperature drop is affected by the latitude. While the southern parts of the Caspian Sea, especially the southeast, are the hottest areas, the Middle Caspian has a lower temperature than the rest of the regions. In the spring season, the temperature decreased in the Middle Caspian, and an increase in temperature was observed towards the upper and lower latitudes. While in the autumn season, a decrease in the water surface temperature was observed in the Persian Gulf and in the winter, in the Oman Sea. The monthly temperature trends for the Persian Gulf and the Oman Sea are increasing for 12 months. In the Caspian Sea, the trend of temperature changes in January and December was decreasing and increasing in the rest of the months.Keywords: Sea Surface Temperature, Trend, Caspian Sea, Persian Gulf and the Oman Sea. IntroductionWater surface temperature in open seas and lakes is known as one of the indicators for measuring oceanographic and meteorological features. Ocean-atmosphere interactions and water surface temperatures can have severe effects on the global climate. For example, rising sea temperatures increase the amount of water vapor in the oceans. This water vapor feeds climatic systems and causes heavy snowfall and rain around the world. It is important to identify the amount and also the trend of temperature changes in the open waters of the Persian Gulf and the Oman Sea and their effects on Iran's climatic conditions. It causes a lot of damage to the coastal ecosystem, structures, shipping, and fishing, which is very important. In the present study, due to the importance of temperature changes in the Caspian Sea and Persian Gulf on temperature changes in coastal areas and the south of the country, this temperature change trend is evaluated by using multi-temporal data of AVHRR sensor of the NOAA satellite during the period 1989-2019. These changes are compared to the Caspian Sea, which is located in the north of the country. Materials and MethodsIn this research, the average, seasonal, and annual temperatures were obtained from daily data in ArcGIS 10.8 software. Then, the trends of the Persian Gulf and the Oman Sea were compared with the Caspian Sea. The daily data of this study were obtained from the AVHRR sensor on a daily basis. The data format is raster. The waters of the Caspian Sea, the Persian Gulf, and the Oman Sea were extracted for 30 years. Research FindingsAccording to the results of the temperature maps, the coldest season of the year is winter in the Persian Gulf and the Oman Sea with an average temperature of 21.5 degrees, and the warmest season is summer with an average temperature of 31.5 degrees. In terms of monthly temperature changes, the Caspian region shows a decreasing trend in January and also the same trend is observed for the month of December, but such a trend was not seen in the Persian Gulf and the Oman Sea. In other words, the trends are quite increasing for 12 months. Discussion of Results and ConclusionWater surface temperature is one of the main variables known to create energy exchanges at sea level. Since seas and oceans have a high heat capacity, they play an important role in the global climate system. The results of this research show that the water surface temperature in the southern water areas of Iran, i.e. the Persian Gulf and the Oman Sea, is increasing. In addition, considering the seasonal average, just like the Caspian Sea, the temperatures show a completely increasing trend. However, in terms of spatial changes, the winter season is not similar to other seasons. In other words, the Caspian Sea does not follow the changes in latitude in winter and shows an opposite pattern, that is, as the latitude increases, the temperature shows an increase. According to the results of this research, it is suggested that in future studies, the process of changes in the water surface temperature of the Mediterranean Sea and its role in the fall and winter rainfall in Iran be evaluated. The comparison of the water surface temperature of the Persian Gulf and the Oman Sea with the Arabian Sea and its effect on Iran's heavy rains is the other suggestion for future studies.
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